A blue, international doing badly (6)
I believe the answer is:
indigo
'a blue' is the definition.
(thesaurus)
'international doing badly' is the wordplay.
'international' becomes 'i' (abbreviation eg in IMF).
'badly' is an anagram indicator.
'doing' is an anagram of 'ndigo'.
'i'+'ndigo'='INDIGO'
(Other definitions for indigo that I've seen before include "Tropical plant" , "Adulthood" , "Colour - I'd go in (anag)" , "supplier of blue stuff" , "A deep blue dye or colour" .)