A ringer perhaps for big Ben has a few hours to kill (4,2,3'1,5) (4,2,4,5)
I believe the answer is:
time on ones hands
'a ringer perhaps for big ben' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'has a few hours to kill 423'15' is the wordplay.
I cannot really see how this works, but
an anagram of 'has' is 'sha' which is present in the answer.
'few' could be 'i' and 'i' is found in the answer.
'kill' could be 'end' (I've seen this in another clue) and 'end' is located in the remaining letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for time on ones hands that I've seen before include "opportunity for relaxation" , "Left with this" , "Wristwatch supplies this" .)