Button hats over hair (4,4)
I believe the answer is:
'button' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'hats over hair' is the wordplay.
'hats' becomes 'caps' (cap is a type of hat).
'over' is a charade indicator (letters next to each other) (in a down clue, some letters go over others).
'hair' becomes 'lock' (lock is a kind of hair).
Can you help me to learn more?