Insect turning up in cloth tomorrow (4)
I believe the answer is:
moth
'insect' is the definition.
(moth is a kind of insect)
'turning up in cloth tomorrow' is the wordplay.
'turning up' says the letters should be written in reverse.
'in' indicates a hidden word.
'htom' is hidden in the letters of 'cloth tomorrow'.
'htom' reversed gives 'MOTH'.
(Other definitions for moth that I've seen before include "Insect attracted to light" , "Night flier" , "Small insect that lays its eggs in cloth or fabric" , "Insect; MND fairy" , "Insect, mainly nocturnal" .)