Rising area is a regret for this land mass (7)
I believe the answer is:
eurasia
'this land mass' is the definition.
(I've seen this before)
'rising area is a regret' is the wordplay.
'rising' is a reversal indicator (going up in a down clue).
'area' becomes 'a' (maths abbreviation).
'regret' becomes 'rue' (synonyms).
'a'+'is'+'a'+'rue'='aisarue'
'aisarue' written backwards gives 'EURASIA'.
'for' is the link.
(Other definitions for eurasia that I've seen before include "Two continents considered as one" , "Landmass extending from Cape Roca in the west to Cape Dezhnev in the east" , "Large expanse of land" , "Land mass - use aria (anag)" , "combination of continents" .)