Reference to ailment is revolting (11)
I believe the answer is:
testimonial
'reference' is the definition.
(I've seen this before)
'to ailment is revolting' is the wordplay.
'revolting' is an anagram indicator.
'to'+'ailment'+'is'='toailmentis'
'toailmentis' is an anagram of 'TESTIMONIAL'.
(Other definitions for testimonial that I've seen before include "A written character" , "Character recommendation - tribute for service" , "Commendation" , "Tribute or token of respect" , "special match" .)