Admission from Conservatives on board a European ship (6)
I believe the answer is:
access
'admission' is the definition.
(I've seen this before)
'conservatives on board a european ship' is the wordplay.
'conservatives' becomes 'cc' (an abbreviation for Conservative written twice).
'on board' is an insertion indicator (inserted letters are taken on board).
'european' becomes 'E' (abbreviation e.g. EU).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'a'+'e'='ae'
'cc' placed within 'ae' is 'acce'.
'acce'+'ss'='ACCESS'
'from' acts as a link.
(Other definitions for access that I've seen before include "Right or way to enter" , "Retrieve information" , "Entrance or passage" , "Credit" , "Entry (code)" .)