Rescue devices for 51 cats (9)
I believe the answer is:
lifelines
'rescue devices' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Perhaps there's a link between them I don't understand?
'51 cats' is the wordplay.
'51' becomes 'LI' (roman numeral).
'cats' becomes 'felines' (I've seen this before).
'li'+'felines'='LIFELINES'
'for' is the link.
Can you help me to learn more?
(Other definitions for lifelines that I've seen before include "Means to rescue" , "May 23 [COME TO THE RESCUE], these" .)