Number working there (5)
I believe the answer is:
three
'number' is the definition.
(three is a number)
'working there' is the wordplay.
'working' indicates anagramming the letters.
'there' is an anagram of 'THREE'.
(Other definitions for three that I've seen before include "Snooker score for potting green ball" , "trilogy" , "Start to count back, briefly" , "Sixth root of seven hundred and twenty nine" , "Number of strikes before you're out" .)