Unhappy about dud sterling (11)
I believe the answer is:
disgruntled
'unhappy' is the definition.
(I've seen this before)
'about dud sterling' is the wordplay.
'about' is an anagram indicator.
'dud'+'sterling'='dudsterling'
'dudsterling' is an anagram of 'DISGRUNTLED'.
(Other definitions for disgruntled that I've seen before include "Grumpy" , "Unhappy" , "Sulking" , "Angry or dissatisfied" , "Cheesed off" .)