Popular, a couple of lines taken together (2,3)
I believe the answer is:
in all
'taken together' is the definition.
(I've seen this in another clue)
'popular a couple of lines' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'couple of lines' becomes 'll' (two abbreviations for line).
'in'+'a'+'ll'='IN ALL'
(Other definitions for in all that I've seen before include "without exception" , "Taken as a whole" , "totally" , "Taken together" , "In total" .)