Going off to get a coin to telephone (7)
I believe the answer is:
souring
'going off' is the definition.
The definition and answer can be both related to change as well as being present participle verbs.
Maybe there's a link between them I don't understand?
'get a coin to telephone' is the wordplay.
'get' means one lot of letters go next to another.
'a coin' becomes 'sou' (sou is a kind of coin).
'to telephone' becomes 'ring' ('ring' can be a synonym of 'telephone').
'sou' put next to 'ring' is 'SOURING'.
'to' acts as a link.
Can you help me to learn more?
(Another definition for souring that I've seen is " Going off (like milk)".)