Couple of pints initially consumed by roofer, habitual drinker (7)
I believe the answer is:
tippler
'habitual drinker' is the definition.
(I've seen this before)
'couple of pints initially consumed by roofer' is the wordplay.
'couple of' says to double the letters.
'initially' indicates taking the first letters.
'consumed by' means one lot of letters goes inside another.
'roofer' becomes 'tiler' (I've seen this before).
The first letter of 'pints' is 'p'.
'p' doubled is 'pp'.
'pp' put inside 'tiler' is 'TIPPLER'.
(Other definitions for tippler that I've seen before include "Imbiber" , "Heavy drinker" , "One habitually drinking" , "Habitual drinker" , "Drunk" .)