Wearing black, tango perfectly balanced (6)
I believe the answer is:
stable
'perfectly balanced' is the definition.
(stable can mean balanced or steady)
'wearing black tango' is the wordplay.
'wearing' means one lot of letters goes inside another.
'black' becomes 'sable' (heraldic term for black).
'tango' becomes 'T' (phonetic alphabet: alpha, bravo, charlie etc.).
'sable' placed around 't' is 'STABLE'.
(Other definitions for stable that I've seen before include "Place of birth" , "Bleats in a horse-house" , "Bleats (anag)" , "Not wobbly" , "Standing firm" .)