Reserve mare damaged Noah's boat (7)
I believe the answer is:
earmark
'reserve' is the definition.
(I know that reserve can be written as earmark)
'mare damaged noah's boat' is the wordplay.
'damaged' indicates anagramming the letters.
'noah's boat' becomes 'ark' (I've seen this in another clue).
'mare' anagrammed gives 'earm'.
'earm'+'ark'='EARMARK'
(Other definitions for earmark that I've seen before include "Set aside for future use" , "Designate funds for a particular purpose" , "Reserve for a particular purpose" , "It identifies the outcome" , "Set aside specifically" .)