Catcalls heard, finished drinking session (5-2)
I believe the answer is:
booze-up
'drinking session' is the definition.
(I've seen this before)
'catcalls heard finished' is the wordplay.
'catcalls' becomes 'boos' (I've seen this before).
'heard' indicates a 'sounds like' (homophone) clue.
'finished' becomes 'up' (eg 'time's up' means the time is finished).
'boos' sounds like 'booze'.
'booze'+'up'='BOOZE-UP'
(Other definitions for booze-up that I've seen before include "Drinking spree" , "Bout of serious drinking" , "Heavy drinking session" .)