Give up because you promise to (8)
I believe the answer is:
forswear
'give up' is the definition.
(I've seen this before)
'because you promise to' is the wordplay.
I cannot really see how this works, but
'because' could be 'for' (I've seen this before) and 'for' is present in the answer.
'promise' could be 'swear' (I've seen this before) and 'swear' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for forswear that I've seen before include "Denounce" , "Retract - recant" , "Renounce upon oath - far worse (anag)" , "Agree to do without" , "Deny on oath" .)