Singer on grass penning epitaph for old English song (6,4)
I believe the answer is:
cherry ripe
'old english song' is the definition.
(traditional song)
'singer on grass penning epitaph' is the wordplay.
'singer on' becomes 'cher' (I can't explain this - if you can you should give a lot more credence to this answer).
'grass' becomes 'rye' (I've seen this before).
'penning' indicates putting letters inside.
'epitaph' becomes 'RIP' (rest in peace).
'rye' enclosing 'rip' is 'ryripe'.
'cher'+'ryripe'='CHERRY RIPE'
'for' is the link.
(Other definitions for cherry ripe that I've seen before include "Julia had to face" , "Song with words by Herrick" .)