Lose your rag as rubbish son needs to get up (4)
I believe the answer is:
snap
'lose your rag' is the definition.
I can't judge whether this defines the answer.
'rubbish son needs to get up' is the wordplay.
'rubbish' becomes 'pan' (both can mean to criticise heavily).
'son needs' becomes 's' (I can't justify this - if you can you should believe this answer much more).
'to get up' says the letters should be written in reverse.
'pan'+'s'='pans'
'pans' backwards is 'SNAP'.
'as' acts as a link.
Can you help me to learn more?
(Other definitions for snap that I've seen before include "Still" , "Simple card-game" , "Break off - card-game" , "Break - children's card game" , "Card game for children" .)