Man on board converted tons to make capital (8)
I believe the answer is:
kingston
'capital' is the definition.
(Kingston is an example)
'man on board converted tons' is the wordplay.
'man on board' becomes 'king' (chess).
'converted' indicates an anagram.
'tons' with letters rearranged gives 'ston'.
'king'+'ston'='KINGSTON'
'to make' acts as a link.
(Other definitions for kingston that I've seen before include "Jamaican capital" , "Royal borough on river Thames" , "island capital" , "Capital of Jamaica" .)