Bit of a snooze then back by six (4,1,5)
I believe the answer is:
half a dozen
'six' is the definition.
(synonyms)
'bit of a snooze then back' is the wordplay.
'bit of' becomes 'halfa' (I can't explain this - if you can you should believe this answer much more).
'a snooze' becomes 'doze' (I've seen this before).
'back' says to take the final letters.
The final letter of 'then' is 'n'.
'halfa'+'doze'+'n'='HALF-A-DOZEN'
'by' acts as a link.
Can you help me to learn more?
(Another definition for half a dozen that I've seen is " six".)