What it takes to tango (3)
I believe the answer is:
two
'what it takes to tango' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for two that I've seen before include "''... turtle doves''" , "Figure" , "Old song 'Tea for . . .'" , "not very many" , "Pair, deuce" .)