Spoils the picture when a transport service is interrupted left and right (5)
I believe the answer is:
blurs
'spoils the picture' is the definition.
The answer and definition can be both related to change as well as being verbs in their -s form.
Perhaps you can see an association between them that I don't see?
'a transport service is interrupted left and right' is the wordplay.
I cannot quite understand how this works, but
'left' could be 'l' (common abbreviation) and 'l' is found within the answer.
'right' could be 'r' (common abbreviation) and 'r' is found in the answer.
'transport' could be 'bus' (bus is a kind of transport) and 'bus' is found within the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
'when' is the link.
Can you help me to learn more?
(Another definition for blurs that I've seen is " Makes less distinct".)