Constant contributor to employ alumni (5)
I believe the answer is:
loyal
'constant' is the definition.
(thesaurus)
'contributor to employ alumni' is the wordplay.
'contributor to' says the answer is hidden in the clue (the letters of the answer contribute to the clue).
'LOYAL' is hidden in the letters of 'employ alumni'.
(Other definitions for loyal that I've seen before include "firm in solidarity" , "Showing firm allegiance" , "Showing enduring firm support" , "Dedicated" , "Faithful - reliable" .)