Ordain following move back and forth (5)
I believe the answer is:
frock
'ordain' is the definition.
(thesaurus)
'following move back and forth' is the wordplay.
'following' becomes 'f' (used when citing page numbers etc).
'move back and forth' becomes 'rock' (rocking is a kind of moving back and forth).
'f'+'rock'='FROCK'
(Other definitions for frock that I've seen before include "Demon" , "Long gown worn by priests; woman's dress" , "something to put on" , "Party dress?" .)