Pair interrupting witness for binge (5)
I believe the answer is:
spree
'for binge' is the definition.
(I've seen this before)
'pair interrupting witness' is the wordplay.
'pair' becomes 'pr' (abbreviation).
'interrupting' is an insertion indicator.
'witness' becomes 'see' (synonyms).
'pr' inserted into 'see' is 'SPREE'.
(Other definitions for spree that I've seen before include "Junket" , "Session of over-indulgence" , "Jollification" , "Merry frolic" , "A lively extravagant outing" .)