Appoint Ian and Rod, possibly (6)
I believe the answer is:
ordain
'appoint' is the definition.
(I've seen this in another clue)
'ian and rod possibly' is the wordplay.
'and' says to put letters next to each other.
'possibly' is an anagram indicator.
'ian'+'rod'='ianrod'
'ianrod' is an anagram of 'ORDAIN'.
(Other definitions for ordain that I've seen before include "Either prescribe" , "Officially order" , "Elevate or appoint to priesthood" , "Invest with priestly authority" , "Make a decree" .)