Unstable new currency gets nervous reaction (8)
I believe the answer is:
neurotic
'unstable' is the definition.
(thesaurus)
'new currency gets nervous reaction' is the wordplay.
'new' becomes 'n'.
'currency' becomes 'euro' (I've seen this before).
'gets' means one lot of letters go next to another.
'nervous reaction' becomes 'tic' (I've seen this in other clues).
'n'+'euro'+'tic'='NEUROTIC'
(Other definitions for neurotic that I've seen before include "Paranoid" , "Abnormally obsessive" , "Affected with emotional disorder" , "Emotionally disturbed" , "I counter in being subject to abnormal anxieties" .)