Habitually drink tea, mostly outside work (4)
I believe the answer is:
tope
'habitually drink' is the definition.
(to tope is to regularly drink alcohol)
'tea mostly outside work' is the wordplay.
'mostly' means to remove the last letter.
'outside' means one lot of letters goes inside another.
'work' becomes 'op' (abbreviation for opus).
'tea' with its final letter removed is 'te'.
'te' enclosing 'op' is 'TOPE'.
(Other definitions for tope that I've seen before include "Drink hard regularly" , "Drink heavily" , "Drink excessively like poet" , "Drink too much like poet" , "Drink a lot like poet" .)