Remove five hundred and switch position (4)
I believe the answer is:
doff
'remove' is the definition.
(I've seen this before)
'five hundred and switch position' is the wordplay.
'five hundred' becomes 'd' (Roman numeral for 500).
'and' is a charade indicator (letters next to each other).
'switch position' becomes 'off' (I've seen this in another clue).
'd'+'off'='DOFF'
(Other definitions for doff that I've seen before include "Take off hat as mark of respect" , "Remove (e.g. hat)" , "Lift (one's hat)" , "Remove one's cap" , "Remove, hat say" .)