Rubbish out on a lawn, initially (5)
I believe the answer is:
offal
'rubbish' is the definition.
(I've seen this in another clue)
'out on a lawn initially' is the wordplay.
'out' becomes 'off' (I've seen this before).
'on' is a charade indicator (letters next to each other).
'initially' suggests taking the first letters.
The first letter of 'lawn' is 'l'.
'off'+'a'+'l'='OFFAL'
(Other definitions for offal that I've seen before include "Waste matter" , "Animal entrails and internal organs as rubbish" , "Bits of waste meat" , "Butcher's stock" , "Meat product" .)