Leaders from Tooting and Walthamstow chill now and again (5)
I believe the answer is:
twice
'again' is the definition.
(I've seen this in another clue)
'leaders from tooting and walthamstow chill' is the wordplay.
'leaders from' suggests taking the first letters.
'and' says to put letters next to each other.
'walthamstow' becomes 'w' (this might be a standard abbreviation I've not previously seen).
'chill' becomes 'ice' (icing is a kind of chilling).
The first letter of 'tooting' is 't'.
't'+'w'+'ice'='TWICE'
'now and' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for twice that I've seen before include "Two times" , "You only live -- (film)" , "Double in quantity" , "Doubly" .)