And, back in slumber, snatch .... (6)
I believe the answer is:
kidnap
'snatch' is the definition.
(I know that snatch can be written as kidnap)
'and back in slumber' is the wordplay.
'back' says the letters should be written in reverse.
'in' means one lot of letters goes inside another.
'slumber' becomes 'kip' (synonyms).
'and' back-to-front is 'dna'.
'dna' going into 'kip' is 'KIDNAP'.
(Other definitions for kidnap that I've seen before include "Small island" , "Abduct and hold for ransom" , "'Abduct, snatch (6)'" , "Abduct (a person)" , "Take person prisoner for ransom" .)