Last at 'Aydock OK? (7)
I believe the answer is:
endorse
'ok?' is the definition.
(I know that endorse is a more specific form of back)
'last at 'aydock' is the wordplay.
I cannot really see how this works, but
'last' could be 'end' (I've seen this in another clue) and 'end' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for endorse that I've seen before include "Ratify" , "Approve of, sign on back as of cheque" , "Put one's name to, approve" , "'Approve of, back (7)'" , "Give public approval of (something)" .)