Roughly handle and finish small bits of mutton (5,4)

'mutton' is the definition.
I know nothing about this answer so I can't tell whether this works.

'roughly handle and finish small bits of' is the wordplay.
'roughly handle' becomes 'scrag' (I can't justify this - if you can you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'finish' becomes 'end' (synonyms).
'bits of' indicates taking the first letters (I've seen 'bit of' mean this).
The first letter of 'small' is 's'.
'scrag'+'end'+'s'='SCRAG-ENDS'

Can you help me to learn more?