Disturb a portal outside it (7)
I believe the answer is:
agitate
'disturb' is the definition.
(I know that disturb can be written as agitate)
'a portal outside it' is the wordplay.
'portal' becomes 'gate' (I've seen this before).
'outside' is an insertion indicator.
'gate' going around 'it' is 'gitate'.
'a'+'gitate'='AGITATE'
(Other definitions for agitate that I've seen before include "Disturb, cause to worry" , "'Stir, excite (7)'" , "rock" , "Stir (up public opinion?)" , "Make nervous; stir" .)