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.
(as in 'bah humbug!')
'a bit of a job ahead' is the wordplay.
'a bit of' indicates the answer is hidden within the clue.
'BAH' is hidden within 'job ahead'.
'when there's' 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" .)