Concession where ocean wall collapses (9)
I believe the answer is:
allowance
'concession' is the definition.
(I've seen this before)
'ocean wall collapses' is the wordplay.
'collapses' indicates anagramming the letters.
'ocean'+'wall'='oceanwall'
'oceanwall' with letters rearranged gives 'ALLOWANCE'.
'where' is the link.
(Other definitions for allowance that I've seen before include "Fixed sum given regularly" , "An amount granted for a period" , "Alloted share" , "Stipend" , "Allotted share" .)