Amount that can be carried by hospital is noxious (7)
I believe the answer is:
harmful
'noxious' is the definition.
('harmful' can be a synonym of 'noxious')
'amount that can be carried by hospital' is the wordplay.
'amount that can be carried' becomes 'armful'.
'by' means one lot of letters go next to another.
'hospital' becomes 'h'.
'armful' after 'h' is 'HARMFUL'.
'is' is the link.
(Other definitions for harmful that I've seen before include "Noxious" , "Dangerous, damaging" , "Injurious" , "Half rum (anag.)" , "Causing injury or damage, say poison or malice" .)