Damage shoreline heartlessly (4)
I believe the answer is:
cost
'damage' is the definition.
(thesaurus)
'shoreline heartlessly' is the wordplay.
'shoreline' becomes 'coast' (I've seen this before).
'heartlessly' means to remove the middle letters.
'coast' with its centre removed is 'COST'.
(Other definitions for cost that I've seen before include "Come to" , "Estimate the expense of doing" , "Outlay required to buy" , "Be priced at" , "estimate price" .)