Trio working there (5)
I believe the answer is:
three
'trio' is the definition.
('three' can be a synonym of 'trio')
'working there' is the wordplay.
'working' indicates anagramming the letters.
'there' anagrammed gives 'THREE'.
(Other definitions for three that I've seen before include "Feet in 3 Down" , "Trinity, triad" , "Amount in a trio" , "Number constituting a crowd?" , "Number of strikes before you're out" .)