Fearless international agent with notion only half formed (8)
I believe the answer is:
intrepid
'fearless' is the definition.
(synonyms)
'international agent with notion only half formed' is the wordplay.
'international' becomes 'int' (abbreviation for international).
'agent' becomes 'rep' (short for representative).
'with' says to put letters next to each other.
'notion' becomes 'idea' (I've seen this before).
'only half formed' indicates taking half.
'idea' with half the letters taken is 'id'.
'int'+'rep'+'id'='INTREPID'
(Other definitions for intrepid that I've seen before include "Bold" , "I printed this way, being daring" , "Fearless, adventurous" , "Brave and fearless" , "Afraid not" .)