Liver and kidneys, say, not available, entirely running short (5)
I believe the answer is:
offal
'liver and kidneys' is the definition.
I can't tell whether this defines the answer.
'not available entirely running short' is the wordplay.
'not available' becomes 'off' (eg the power might be off).
'entirely' becomes 'all' (all can mean entirely or completely).
'running short' means to remove the last letter.
'all' with its last letter taken off is 'al'.
'off'+'al'='OFFAL'
'say' is the link.
Can you help me to learn more?
(Other definitions for offal that I've seen before include "Carrion" , "Internal organs of an animal some find tasty" , "Bits of waste meat" , "Trimmings of a butchered animal" , "Waste parts of a carcass" .)