Set of drinks including Tango makes you plump (6)
I believe the answer is:
rotund
'plump' is the definition.
(I've seen this before)
'set of drinks including tango' is the wordplay.
'set of drinks' becomes 'round' (as in a round of drinks ordered at a bar).
'including' is an insertion indicator.
'tango' becomes 'T' (phonetic alphabet: alpha, bravo, charlie etc.).
'round' going around 't' is 'ROTUND'.
'makes you' is the link.
(Other definitions for rotund that I've seen before include "Large and plump" , "Spherical" , "Rather obese" , "Tubby" , "Portly" .)