Makes up for having no seat, maybe (6)
I believe the answer is:
atones
'makes up for' is the definition.
(I've seen this in another clue)
'no seat maybe' is the wordplay.
'maybe' indicates an anagram.
'no'+'seat'='noseat'
'noseat' is an anagram of 'ATONES'.
'having' is the link.
(Other definitions for atones that I've seen before include "Makes up for, say sin" , "Makes redress" , "Makes amends using a stone" , "Makes amends for sin" , "Makes up for wrong done with a stone" .)