Clear manager finally dismissed over order to quit the hard stuff (5,2)
I believe the answer is:
sober up
'order to quit the hard stuff' is the definition.
'clear manager finally dismissed over' is the wordplay.
'clear' becomes 'pure' ('pure' can be similar in meaning to 'clear').
'manager' becomes 'boss' (I've seen this before).
'finally dismissed' means to remove the last letter.
'over' is a reversal indicator.
'pure'+'boss'='pureboss'
'pureboss' with its final letter removed is 'purebos'.
'purebos' backwards is 'SOBER UP'.
(Other definitions for sober up that I've seen before include "Get real" , "What you do when drink wears off" , "become serious" , "Become less drunk" .)