Extra flexible chaps leading tango (10)
I believe the answer is:
supplement
'extra' is the definition.
(I've seen this before)
'flexible chaps leading tango' is the wordplay.
'flexible' becomes 'supple' ('supple' can be similar in meaning to 'flexible'**).
'chaps' becomes 'men' (I've seen this before).
'leading' suggests taking the first letters.
The initial letter of 'tango' is 't'.
'supple'+'men'+'t'='SUPPLEMENT'
(Other definitions for supplement that I've seen before include "Extra" , "Add to; newspaper section" , "Boost" , "Something added" , "addition" .)