Performing duets with one was appropriate (6)
I believe the answer is:
suited
'appropriate' is the definition.
(synonyms)
'performing duets with one' is the wordplay.
'performing' is an anagram indicator (the letters move around or 'perform').
'with' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'duets' is an anagram of 'suted'.
'suted' placed around 'i' is 'SUITED'.
'was' is the link.
(Other definitions for suited that I've seen before include "Appropriate, fitting" , "Well adapted" , "agreed" , "Befitted" , "Matched" .)