Knowing conga isn't unusual (9)
I believe the answer is:
cognisant
'knowing' is the definition.
'conga isn't unusual' is the wordplay.
'unusual' indicates an anagram.
'conga'+'isnt'='congaisnt'
'congaisnt' with letters rearranged gives 'COGNISANT'.
(Other definitions for cognisant that I've seen before include "Aware of" , "Having knowledge or understanding" , "Knowledgeable" .)