... and, wearing a hat, 50% leave (7)
I believe the answer is:
abandon
'leave' is the definition.
(abandoning is a kind of leaving)
'and wearing a hat 50' is the wordplay.
'wearing' means one lot of letters goes inside another.
'hat 50' becomes 'bon' (I can't justify this - if you can you should give a lot more credence to this answer).
'a'+'bon'='abon'
'and' inserted within 'abon' is 'ABANDON'.
Can you help me to learn more?
(Other definitions for abandon that I've seen before include "Desert; lack of restraint" , "Completely give up; desert" , "Leave, desert" , "Desert; give up (action)" , "Give up (something) completely" .)