Clique of horse traders? (3)
I believe the answer is:
set
'clique' is the definition.
(thesaurus)
'of horse traders?' is the wordplay.
'of' indicates the answer is hidden within the clue.
'SET' is hidden within 'horse traders'.
(Other definitions for set that I've seen before include "Major segment of tennis match" , "Determined or congealed" , "Fixed; collection" , "become firm" , "number of games" .)