Comedy not half seen: Everyman's suppressing tantrum over IT, getting aggressive (11)
I believe the answer is:
competitive
'aggressive' is the definition.
(similar in meaning)
'comedy not half seen everyman's' is the wordplay.
'not half' means to take half the letters.
'seen' becomes 'petit' (I can't justify this - if you can you should believe this answer much more).
'everyman's' becomes 'I've' (where the crossword setter is 'Everyman').
'comedy' halved is 'com'.
'com'+'petit'+'ive'='COMPETITIVE'
'suppressing tantrum over it getting' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Another definition for competitive that I've seen is " Combative, vying".)