Payment I rejected, in part or whole (6)
I believe the answer is:
entire
'whole' is the definition.
('entire' can be similar in meaning to 'whole')
'payment i rejected in part' is the wordplay.
'in part' indicates a hidden word.
'ENTIRE' can be found hidden inside 'payment i rejected'.
'or' is the link.
(Other definitions for entire that I've seen before include "Whole; unbroken" , "outright" , "Whole; absolute" , "Full, intact" , "Envelope" .)