Excuse made by Tuck, endlessly? (4)
I believe the answer is:
plea
'excuse' is the definition.
(thesaurus)
'tuck endlessly?' is the wordplay.
'tuck' becomes 'pleat' (I've seen this before).
'endlessly?' means to remove the last letter (I've seen 'endlessly' mean this).
'pleat' with its last letter removed is 'PLEA'.
'made by' acts as a link.
(Other definitions for plea that I've seen before include "Excuse, entreaty" , "Request for mercy?" , "Excuse - pretext" , "Leap (anag.)" , "Answer made by the accused to the charge" .)