Turner ultimately following John Constable? (7)
I believe the answer is:
officer
'constable?' is the definition.
(police officer)
'turner ultimately following john' is the wordplay.
I cannot quite understand how this works, but
'following' could be 'ff' (abbreviation used in citations) and 'ff' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for officer that I've seen before include "One holding post" , "Police(wo)man" , "Committee member" , "who has a public position" , "Person with commission in armed services" .)