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 an anagram.
'there' anagrammed gives '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" .)