Undecided and nervous about tango (7)
I believe the answer is:
neutral
'undecided' is the definition.
'nervous about tango' is the wordplay.
'nervous' becomes 'neural' ('neural' can be a synonym of 'nervous').
'about' is an insertion indicator.
'tango' becomes 't' (phonetic alphabet: alpha, bravo, charlie etc.).
'neural' going around 't' is 'NEUTRAL'.
'and' is the link.
(Other definitions for neutral that I've seen before include "Renault altered" , "uncommitted to either side" , "Impersonal, inert" , "Unaligned" , "Grey" .)