Big characters from Sunday Times and Times should provide relief (5-2)
I believe the answer is:
stand-by
'sunday times and times should provide relief' is the definition.
I can't tell whether this defines the answer.
'big characters from' is the wordplay.
'big characters' becomes 'stand' (I can't justify this - if you can you should believe this answer much more).
'from' becomes 'by' (by can mean from a particular person).
'stand'+'by'='STAND-BY'
Can you help me to learn more?
(Other definitions for stand-by that I've seen before include "Quiescent state" , "Something kept in readiness" .)