Eat quickly standing - and not slouching (4,7)
I believe the answer is:
bolt upright
'not slouching' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'eat quickly standing' is the wordplay.
'eat quickly' becomes 'bolt' (I've seen this before).
'standing' becomes 'upright' (I've seen this before).
'bolt'+'upright'='BOLT UPRIGHT'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for bolt upright that I've seen before include "In alert mode" , "Standing stiffly" , "Rigidly erect" , "Definitely not slouching" .)