Line adopted by new literary big guns (9)
I believe the answer is:
artillery
'big guns' is the definition.
(I've seen this before)
'line adopted by new literary' is the wordplay.
'line' becomes 'l'.
'adopted by' means one lot of letters goes inside another (I've seen this in other clues).
'new' indicates anagramming the letters.
'literary' anagrammed gives 'artilery'.
'l' inserted into 'artilery' is 'ARTILLERY'.
(Other definitions for artillery that I've seen before include "Powerful guns" , "Army unit that uses big guns" , "Large guns for army in land war" , "Ordnance" , "Large-calibre guns" .)