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' acts as a 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" .)