Insurance for a hundred and more (5)
I believe the answer is:
cover
'insurance' is the definition.
(I've seen this before)
'hundred and more' is the wordplay.
'hundred' becomes 'c' (Roman numeral).
'and' is a charade indicator (letters next to each other).
'more' becomes 'over' (I've seen this before).
'c'+'over'='COVER'
'for a' is the link.
(Other definitions for cover that I've seen before include "Lid, travel (distance)" , "Disguise" , "Encompass" , "Fielder" , "(Put) lid (on) - fielding position - insurance" .)