He's mad to give a supporter a half ticket (7)
I believe the answer is:
fanatic
'he's mad to' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'a supporter a half ticket' is the wordplay.
'a supporter' becomes 'fan' (fan is a kind of supporter).
'half' indicates taking half.
'ticket' halved is 'tic'.
'fan'+'a'+'tic'='FANATIC'
'give' is the link.
Can you help me to learn more?
(Other definitions for fanatic that I've seen before include "One motivated by irrational enthusiasm" , "Bigot - enthusiast" , "Excessively devoted" , "crank" , "enthusiastic" .)