Noticed I raced round (5)
I believe the answer is:
spied
'noticed' is the definition.
(I've seen this before)
'i raced round' is the wordplay.
'raced' becomes 'sped' ('speed' can be a synonym of 'race').
'round' means one lot of letters goes inside another.
'i' going into 'sped' is 'SPIED'.
(Other definitions for spied that I've seen before include "Saw" , "Spotted" , "Caught sight of" , "Seen" , "Was a secret agent" .)