The two in limbo there (4)
I believe the answer is:
both
'the two' is the definition.
(synonyms)
'in limbo there' is the wordplay.
'in' indicates a hidden word.
'BOTH' can be found hidden inside 'limbo there'.
(Other definitions for both that I've seen before include "The one and the other" , "couple" , "The two (things)" , "Two considered together" , "Each of two (alternatives)" .)