Refer to some illicit encounter (4)
I believe the answer is:
cite
'refer to' is the definition.
(synonyms)
'some illicit encounter' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'CITE' is hidden in the letters of 'illicit encounter'.
(Other definitions for cite that I've seen before include "Quote as an example or in support" , "Adduce as proof" , "Mention as example or quote" , "for instance" , "name" .)