Boatman placed between noble and royal persons previously (7)
I believe the answer is:
earlier
'previously' is the definition.
(synonyms)
'boatman placed between noble and royal' is the wordplay.
'boatman' becomes 'ie' (I can't explain this - if you can you should believe this answer much more).
'placed between' means one lot of letters goes inside another.
'noble' becomes 'earl' (earl is a kind of noble).
'and' means one lot of letters go next to another.
'royal' becomes 'r' (abbreviation).
'earl'+'r'='earlr'
'ie' put inside 'earlr' is 'EARLIER'.
'persons' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.
(Other definitions for earlier that I've seen before include "Further in advance" , "in days of yore?" , "Sooner in time" , "Prior" , "at a previous date" .)