Yearn to tango a lot (5)
I believe the answer is:
sight
'a lot' is the definition.
(sight can informally mean a lot of something)
'yearn to tango' is the wordplay.
'yearn' becomes 'sigh' (I've seen this in another clue).
'to tango' becomes 'T' (phonetic alphabet: alpha, bravo, charlie etc.).
'sigh'+'t'='SIGHT'
(Other definitions for sight that I've seen before include "Looking" , "Observe" , "something to behold" , "Aiming device on gun" , "Visual perception" .)