Endorsement is rejected by Midge Ure (9)
I believe the answer is:
signature
'endorsement' is the definition.
(thesaurus)
'is rejected by midge ure' is the wordplay.
'rejected' says the letters should be written in reverse.
'by' means one lot of letters go next to another.
'midge' becomes 'gnat' (I've seen this before).
'is' in reverse letter order is 'si'.
'si'+'gnat'+'ure'='SIGNATURE'
(Other definitions for signature that I've seen before include "Identifying script" , "Distinctive characteristic" , "Squiggle perhaps" , "time indicated by this?" , "Distinctive mark" .)