A good sleuth probes Middle East collector (6)
I believe the answer is:
magpie
'collector' is the definition.
(magpie is a kind of collector)
'a good sleuth probes middle east' is the wordplay.
'good' becomes 'g' (abbreviation).
'sleuth' becomes 'pi' (private investigator).
'probes' indicates putting letters inside (probe can mean to poke or prod into).
'middle east' becomes 'me' (abbreviation for Middle East).
'a'+'g'+'pi'='agpi'
'agpi' inserted into 'me' is 'MAGPIE'.
(Other definitions for magpie that I've seen before include "One on target" , "Black and white bird, known as thieving" , "Part of target" , "Common bird" , "A black-and-white thieving bird" .)