Headwear involves Queen in wagers (6)
I believe the answer is:
berets
'headwear' is the definition.
(I know that berets is a type of cap)
'queen in wagers' is the wordplay.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'in' means one lot of letters goes inside another.
'wagers' becomes 'bets' ('bet' can be a synonym of 'wager').
'er' going inside 'bets' is 'BERETS'.
'involves' is the link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for berets that I've seen before include "Round flattish caps" , "capital investments" , "Round flat caps" , "Soft caps with no brim" , "headgear" .)