Cheeseparer, one initially swimming in sea off Nice (5)
I believe the answer is:
miser
'cheeseparer' is the definition.
(both can mean someone ungenerous with money)
'one initially swimming in sea off nice' is the wordplay.
'one' becomes 'i' (Roman numeral**).
'initially' suggests taking the first letters.
'in' indicates putting letters inside.
'sea off nice' becomes 'mer' ('sea' in French, eg in Nice).
The initial letter of 'swimming' is 's'.
'i'+'s'='is'
'is' placed inside 'mer' is 'MISER'.
(Other definitions for miser that I've seen before include "man, that's close" , "Mean-minded type" , "Penny-pinching person like Scrooge" , "Hoarder of money and possessions" , "One such as Scrooge" .)