Unstable northern union leader dressed in blue? (8)
I believe the answer is:
neurotic
'unstable' is the definition.
(thesaurus)
'northern union leader dressed in blue?' is the wordplay.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'leader' suggests taking the first letters.
'dressed in' indicates putting letters inside.
'blue?' becomes 'erotic' (I've seen this before**).
The first letter of 'union' is 'u'.
'u' placed within 'erotic' is 'eurotic'.
'n'+'eurotic'='NEUROTIC'
(Other definitions for neurotic that I've seen before include "Hypersensitive" , "Subject to excessive anxieties and abnormal behaviour" , "I counter in being subject to abnormal anxieties" , "Very anxious and stressed" , "Subject to abnormal anxieties or obsessive behaviour" .)