Rugby player (5,4)
(Another definition for scrum half that I've seen is " Rugby player -- March's flu (anag)".)
(Another definition for stand-off half that I've seen is " Member of rugby XV".)
'rugby player' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for hooker that I've seen before include "Streetwalker" , "Rugby player; prostitute" , "one that heels" , "Rugby centre forward in the ..." , "Rugby player - traditional single-masted Irish working boat" .)