Deputy for some columnist, perhaps (5)
I believe the answer is:
locum
'deputy' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for locum that I've seen before include "Temporary substitute" , "one won't be in position for ever!" , "Someone standing in temporarily for another of the same profession" , "Deputising doctor" , "Stand-in, for a doctor say" .)