It's said to justify soft going on the field (4)
I believe the answer is:
plea
'it's said to justify' is the definition.
I can't judge whether this definition defines the answer.
'soft going on the field' is the wordplay.
'soft' becomes 'p' (musical abbreviation for 'piano').
'going on' says to put letters next to each other.
'the field' becomes 'lea' (lea can mean a meadow or field of grass).
'p'+'lea'='PLEA'
Can you help me to learn more?
(Other definitions for plea that I've seen before include "Guilty perhaps" , "Request - appeal" , "Urgent request" , "Defence - excuse - appeal" , "Request for mercy?" .)