Thief's run inside as client worked (9)
I believe the answer is:
larcenist
'thief's' is the definition.
(larcenist is a kind of thief)
'run inside as client worked' is the wordplay.
'run' becomes 'r' (cricket abbreviation).
'inside' is an insertion indicator.
'worked' is an anagram indicator.
'as'+'client'='asclient'
'asclient' is an anagram of 'lacenist'.
'r' inserted within 'lacenist' is 'LARCENIST'.
(Other definitions for larcenist that I've seen before include "One criminal" , "One takes" , "Person who takes" , "Dishonest person" , "nicker" .)