They should have safety pins in them (8)
I believe the answer is:
grenades
'they' is the definition.
Both the answer and definition are plural nouns.
Maybe there's a link between them I don't understand?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for grenades that I've seen before include "Small bombs thrown by hand" , "Grandees holding small bombs" , "Hand-thrown bombs for grandees" , "Small explosive hand-bomb" , "Small hand-bombs" .)