One longing aloud for a patch of ground (4)
I believe the answer is:
acre
'a patch of ground' is the definition.
(acre is a measurement of land)
'one longing aloud' is the wordplay.
'one longing' becomes 'acher' (someone longing or aching for something).
'aloud' shows a homophone (sound like).
'acher' sounds like 'ACRE'.
'for' acts as a link.
(Other definitions for acre that I've seen before include "region of ground" , "Four roods - Israeli port" , "Unit of land area" , "Imperial unit of area" , "Israeli seaport" .)