Get lost in the rhythm, then I tango (4,2)
I believe the answer is:
beat it
'get lost' is the definition.
(I've seen this before)
'rhythm then i tango' is the wordplay.
'rhythm' becomes 'beat' ('beat' can be a synonym of 'rhythm').
'then' says to put letters next to each other.
'tango' becomes 't' (phonetic alphabet: alpha, bravo, charlie etc.).
'beat'+'i'+'t'='BEAT IT'
'in the' acts as a link.
(Other definitions for beat it that I've seen before include "Clear off!" , "Scarper" , "Get going" , "fly away" , "Slang order to go away, get lost" .)