Mishandle gang overwhelmed by drink (5,2)
I believe the answer is:
screw up
'mishandle' is the definition.
(I know that mishandle can be written as screw up)
'gang overwhelmed by drink' is the wordplay.
'gang' becomes 'crew' (synonyms).
'overwhelmed by' means one lot of letters goes inside another (inserted letters get absorbed or overwhelmed).
'drink' becomes 'sup' (to sup is to drink).
'crew' placed inside 'sup' is 'SCREW-UP'.
(Other definitions for screw up that I've seen before include "Ruin; distort" , "Summon" , "Go badly wrong" , "Fail badly" , "tense" .)