Running behind officer showing some guts (5)
I believe the answer is:
colon
'some guts' is the definition.
(thesaurus)
'running behind officer' is the wordplay.
'running' becomes 'on' (eg when a machine is running it is on).
'behind' says to put letters next to each other.
'officer' becomes 'col' (short for colonel).
'on' put after 'col' is 'COLON'.
'showing' acts as a link.
(Other definitions for colon that I've seen before include "Part of body; two dots" , "Part of the intestine - punctuation mark" , "almost the end of another" , "that may cut sentence" , "Part of intestines" .)