Cambridge college's uprising — can I go outside? (7)
I believe the answer is:
'cambridge college's' is the definition.
(Trinity College is a Cambridge college)
'uprising can i go outside?' is the wordplay.
'uprising can' becomes 'trin' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'go' becomes 'try' (both can mean an attempt).
'outside?' says to hollow out the word (remove centre letters) (I've seen 'outside' mean this).
'try' with its middle taken out is 'ty'.
(Other definitions for trinity that I've seen before include "Holy triad" , "Oxbridge college" , "Term" , "House" , "A group of three people" .)