Conceal a hundred and more (5)
I believe the answer is:
'conceal' is the definition.
(I know that cover is a is a more specific form of the action conceal)
'a hundred and more' is the wordplay.
'a hundred' becomes 'c' (Roman numeral).
'and' is a charade indicator (letters next to each other).
'more' becomes 'over' (I've seen this before).
(Other definitions for cover that I've seen before include "Totally obscure" , "Extend over (an area)" , "Mask, hide" , "Fielder" , "Encompass" .)