Provide for a surplus of 100 (5)
I believe the answer is:
cover
'provide for' is the definition.
(synonyms)
'a surplus of 100' is the wordplay.
I cannot quite see how this works, but
'surplus' could be 'over' (I've seen this before) and 'over' is located in the answer.
'100' could be 'c' (Roman numeral) and 'c' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for cover that I've seen before include "(Put) lid (on) - fielding position - insurance" , "Disguise" , "Encompass" , "Mask, hide" , "the point of cricket" .)