Mean to trim the end off (3)
'mean' is the definition.
(I've seen this before)
'trim the end off' is the wordplay.
'trim' becomes 'pare' (synonyms).
'the end off' means to remove the last letter.
'pare' with its final letter taken off is 'PAR'.
'to' is the link.
(Other definitions for par that I've seen before include "level footing", "Rap for being average", "Norm", "Standard amount", "Average score for good golf player".)