Record-breaking compiler's very relaxed (4)
I believe the answer is:
limp
'very relaxed' is the definition.
(limp can mean relaxed or soft)
'record-breaking compiler's' is the wordplay.
'record' becomes 'L-P' (abbreviation for long play record).
'breaking' is an insertion indicator (inserted letters break into others).
'compiler's' becomes 'im' (I've seen this in other clues).
'lp' going around 'im' is 'LIMP'.
(Other definitions for limp that I've seen before include "without energy" , "Walk stiffly - lacking energy" , "Hanging loosely - hobble" , "Lacking stiffness" , "Hobble, being slack" .)