Ray cheers supporting staff (5)
I believe the answer is:
manta
'ray' is the definition.
(manta is a kind of ray)
'cheers supporting staff' is the wordplay.
'cheers' becomes 'ta' (I've seen this in other clues).
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'staff' becomes 'man' (manning is a kind of staffing).
'ta' after 'man' is 'MANTA'.
(Other definitions for manta that I've seen before include "Devilfish" , "Giant ray" , "Kind of ray" , "Large ray" .)