Force confronted over drink (6)
I believe the answer is:
decaff
'drink' is the definition.
'force confronted over' is the wordplay.
'force' becomes 'f' (symbol used in Physics e.g. f=ma).
'confronted' becomes 'faced' (I've seen this before).
'over' is a reversal indicator.
'f'+'faced'='ffaced'
'ffaced' backwards is 'DECAFF'.
(Other definitions for decaff that I've seen before include "Type of coffee (colloq.)" , "Coffee without the kick" .)