Spotted one being rushed outside (5)
I believe the answer is:
spied
'spotted' is the definition.
('spy' can be a synonym of 'spot')
'one being rushed outside' is the wordplay.
'one' becomes 'i' (Roman numeral).
'being rushed' becomes 'sped' (I've seen this before).
'outside' means one lot of letters goes inside another (some letters go outside others).
'i' going inside 'sped' is 'SPIED'.
(Other definitions for spied that I've seen before include "Watched secretly" , "Seen" , "Was a secret agent" , "Spotted" , "Caught sight of" .)