One local conceals detectives - returning is suggestive (10)
I believe the answer is:
indicative
'is suggestive' is the definition.
(synonyms)
'one local conceals detectives returning' is the wordplay.
'one' becomes 'i' (Roman numeral).
'local' becomes 'native' (relating to a particular area).
'conceals' indicates putting letters inside.
'detectives' becomes 'CID' (abbreviation for Criminal Investigation Department).
'returning' shows that the letters should be reversed in order.
'cid' back-to-front is 'dic'.
'native' enclosing 'dic' is 'ndicative'.
'i'+'ndicative'='INDICATIVE'
(Other definitions for indicative that I've seen before include "Serving as a sign" , "mood" .)