Line to put into program for computer (6)
I believe the answer is:
laptop
'computer' is the definition.
(laptop is a part of computer)
'line to put into program' is the wordplay.
'line' becomes 'l' (used when specifying particular lines from a poem).
'put into' indicates putting letters inside.
'program' becomes 'app' (type of computer program).
'to' inserted into 'app' is 'aptop'.
'l'+'aptop'='LAPTOP'
'for' is the link.
(Other definitions for laptop that I've seen before include "Kind of computer" , "PC" , "Small computer" , "Aid for businessman" , "device?" .)