The same officer is a fool (4)
I believe the answer is:
dolt
'a fool' is the definition.
(thesaurus)
'the same officer' is the wordplay.
'the same' becomes 'do' (abbreviation for ditto).
'officer' becomes 'lt' (I've seen this in other clues).
'do'+'lt'='DOLT'
'is' is the link.
(Other definitions for dolt that I've seen before include "Idiot" , "Blockhead" , "Halfwit" , "Dull or stupid fellow" , "Stupid person" .)