Comedian beset by disappointment — hard to get contract (4,4,4)
I believe the answer is:
come down with
'contract' is the definition.
(synonyms)
'comedian beset by disappointment hard' is the wordplay.
'comedian' becomes 'wit' (a witty person).
'beset by' means one lot of letters goes inside another ('beset' could historically mean 'cover').
'disappointment' becomes 'comedown' (comedown can mean a disappointment or anti-climax).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'comedown'+'h'='comedownh'
'wit' going inside 'comedownh' is 'COME DOWN WITH'.
'to get' acts as a link.
(Another definition for come down with that I've seen is " Contract (a disease)".)