Guys that are fairly dull last to expect flattery (12)
I believe the answer is:
blandishment
'flattery' is the definition.
(blandishment is a kind of flattery)
'guys that are fairly dull last to expect' is the wordplay.
I cannot quite understand how this works, but
'guys' could be 'men' (guy can mean a man) and 'men' is found within the answer.
'are' could be 'a' (short for 'are', historical unit of measurement) and 'a' is found in 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 blandishment that I've seen before include "blarney" , "flattery" , "Wheedling" .)