Big beast in fashion work turned up (5)
I believe the answer is:
hippo
'big beast' is the definition.
(I know that hippo is a type of big beast)
'in fashion work turned up' is the wordplay.
'in fashion' becomes 'hip' (I've seen this in another clue).
'work' becomes 'op' (abbreviation for opus).
'turned up' shows that the letters should be reversed in order.
'op' in reverse letter order is 'po'.
'hip'+'po'='HIPPO'
(Other definitions for hippo that I've seen before include "Large wallower (abbr)" , "One thick-skinned" , "Water-loving mammal" , "Thick-skinned type" , "Massive thick-skinned animal of African rivers" .)