Creature initially employed in Crosby? (5)
I believe the answer is:
being
'creature' is the definition.
(thesaurus)
'initially employed in crosby?' is the wordplay.
'initially' suggests taking the first letters.
'in' is an insertion indicator.
'crosby?' becomes 'bing' (singer Bing Crosby).
The initial letter of 'employed' is 'e'.
'e' going into 'bing' is 'BEING'.
(Other definitions for being that I've seen before include "Person" , "A matter of 9 in the play" , "Living thing" , "Existence" , "Existing" .)