Let's make a change just in case (4)
I believe the answer is:
lest
'just in case' is the definition.
(I've seen this in another clue)
'let's make a change' is the wordplay.
'make a change' is an anagram indicator (I've seen 'making a change' mean this).
'lets' is an anagram of 'LEST'.
(Other definitions for lest that I've seen before include "To avoid the risk that - we forget?" , "In order not to, to avoid the risk that" , "For fear that (something should happen)" , "For fear that; in order to prevent" , "In case" .)