Expression of disgust when there's a bit of a job ahead (3)
I believe the answer is:
bah
'expression of disgust' is the definition.
(I've seen this before)
'there's a bit of a job ahead' is the wordplay.
'there's a bit of' says the answer is hidden in the clue.
'BAH' is hidden within 'job ahead'.
'when' is the link.
(Other definitions for bah that I've seen before include "Appalling!" , "Exclamation of contempt or disgust - Scrooge used to say it" , "''...! Humbug!'' (Scrooge)" , "Expression of disgust or contempt" , "''... Humbug'' Scrooge's cry" .)