Where paw-print cushions may be found: one of them might cause upset? (9)
I believe the answer is:
underdogs
'where paw-print cushions may be found one of them might' is the definition.
The definition suggests a singular noun but the answer is a plural noun.
'cause upset?' is the wordplay.
I cannot really understand how this works, but
'cause' could be 'dog' (dog is a kind of cause) and 'dog' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for underdogs that I've seen before include "unfavoured ones" , "No drudges among those in subordinate positions" , "People expected to lose" .)