Paddy Brown's first to take drink (7)
I believe the answer is:
tantrum
'paddy' is the definition.
(thesaurus)
'brown's first to take drink' is the wordplay.
'brown' becomes 'tan' (tan is a kind of brown).
'first to' says to take the initial letters.
'drink' becomes 'rum' (I've seen this before).
The first letter of 'take' is 't'.
'tan'+'t'+'rum'='TANTRUM'
(Other definitions for tantrum that I've seen before include "Spoilt brat's fit" , "Fit - pet" , "Fit of childish temper" , "Childish fit of rage" , "Burst of temper" .)