Let it stand the test, possibly (4)
I believe the answer is:
stet
'let it stand' is the definition.
(I've seen this in another clue)
'test possibly' is the wordplay.
'possibly' indicates anagramming the letters.
'test' with letters rearranged gives 'STET'.
'the' acts as a link.
(Other definitions for stet that I've seen before include "Ignore instruction to change" , "Let it stand (on proof)" , "marginal instruction" , "Let it stand - printer's mark" , "This must not be changed" .)