Quickly grabs, coming back, a cat nap in it (5,2)

'quickly grabs' is the definition.
'snaps up' can be an answer for 'grabs' ('snap up' can be a synonym of 'grab'). I am unsure of the 'quickly' bit.

'coming back a cat nap in it' is the wordplay.
'coming back' says the letters should be written backwards.
'a cat' becomes 'puss' (puss is a kind of cat).
'in it' indicates putting letters inside.
'puss' back-to-front is 'ssup'.
'ssup' going around 'nap' is 'SNAPS UP'.

Can you help me to learn more?