Crowd or pack (3)
I believe the answer is:
jam
I believe this is a double definition.
'crowd' is the first definition.
(jam is a kind of crowd)
'pack' is the second definition.
(synonyms)
(Other definitions for jam that I've seen before include "Block signals" , "Fruit preserve" , "Preserve; pack tightly" , "Sweet stuff for bread - stuff it in" , "Troublesome situation" .)