Relinquish some grain, they said (4)
I believe the answer is:
cede
'relinquish' is the definition.
(I've seen this before)
'grain they said' is the wordplay.
'grain' becomes 'seed' (I've seen this before).
'they said' indicates a 'sounds like' (homophone) clue.
'seed' sounds like 'CEDE'.
'some' acts as a link.
(Other definitions for cede that I've seen before include "Give up (territory)" , "Surrender or relinquish possession" , "Give up (eg, power)" , "Surrender or yield" , "Yield, give way" .)