Do ask mostly for best (7)
I believe the answer is:
conquer
'best' is the definition.
(I've seen this before)
'do ask mostly' is the wordplay.
I cannot quite see how this works, but
'do' could be 'con' and 'con' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'for' is the link.
Can you help me to learn more?
(Other definitions for conquer that I've seen before include "Gain possession by force" , "Triumph over" , "Miss Hardcastle stoops to" , "Crush" , "Defeat, overcome" .)