Professional association has a thing for cowboys (5)
I believe the answer is:
lasso
'a thing for cowboys' is the definition.
(cowboys use lassoes)
'professional association has' is the wordplay.
'has' indicates a hidden word.
'LASSO' is hidden in the letters of 'professional association'.
(Other definitions for lasso that I've seen before include "A cowboy's rope with a running noose" , "Belgian composer" , "snare" , "Rope for throwing" , "Somehow catch" .)