Give support to ‘ack that came last? (7)
I believe the answer is:
endorse
'give support to' is the definition.
(I've seen this in another clue)
''ack that came last?' 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 may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for endorse that I've seen before include "Put penalty points on (a driving licence)" , "Sore end (anag.)" , "'Approve of, back (7)'" , "Back, sanction" , "Red ones (anag.)" .)