Record to break when finding mountains (4)
I believe the answer is:
alps
'mountains' is the definition.
(European mountain range)
'record to break when' is the wordplay.
'record' becomes 'L-P' (abbreviation for long play record).
'to break' indicates putting letters inside (inserted letters break into the word).
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'lp' put within 'as' is 'ALPS'.
'finding' is the link.
(Other definitions for alps that I've seen before include "South-central European mountain system" , "Slap (anag.)" , "European mountain chain" , "Slap about in mountains" , "With pals in great mountains" .)