Republican occupying post yes-man vacated for Monroe (7)
I believe the answer is:
marilyn
'for monroe' is the definition.
(actress Marilyn Monroe)
'republican occupying post yes-man' is the wordplay.
'republican' becomes 'r' (abbreviation).
'occupying' is an insertion indicator (inserted letters occupy or enter the word).
'post' becomes 'mail' (synonyms).
'yes' becomes 'y'.
'man' becomes 'N' (knight, a man in chess).
'r' inserted within 'mail' is 'maril'.
'maril'+'y'+'n'='MARILYN'
'vacated' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
(Other definitions for marilyn that I've seen before include "1956 Bus Stop star" , "- - Monroe, US film star" , "Hollywood sex icon . . . . . . . Monroe" , "- Monroe, US film actress" .)