Apply for dual citizenship U.K. And Canada to travel to US ESTA free

Is this possible

Afaict assuming you are "first generation abroad" (that is your mother was born in Canad) then yes it should be possible. If your mother was born outside of Canada then things get more complicated.

and will there be any problems?

I don't belive there should be any "problems" per-se, Neither the UK or Canada forbids dual citizenship.

However if your only reason for doing this is to make occasional short tourist/buisness visits to the USA by air and you have not done something that makes you ineligable for the VWP then it's IMO a lot of hassle for virtually no gain. There will likely be far more paperwork and expense involved in Excercising your canadian citizenship than in getting an ESTA.

OTOH if you have become ineligable for the VWP, you want to make longer visits to the USA than the ESTA allows or you want to cross the land borders of the USA frequently* then the Canadian citizenship route may make more sense.

* My understanding is that at land borders Canadians generally get waved through in their cars with minimal checks while VWP travellers have to park up, go into the immigration office and wait in a long queue.

Yes, this is possible. Once you are a Canadian citizen, with a Canadian passport, you will not need an ESTA to enter the US.

However, this is a LOT of cost and effort to go to if your only real purpose is to save $14 every 2 years on obtaining an ESTA. If you are obtaining Canadian citizenship for other reason, then yes, using your Canadian passport to enter the US would make sense. But doing it just to avoid obtaining an ESTA does not.