One’s going to miss tracking European criminal (7)
I believe the answer is:
illegal
'criminal' is the definition.
(similar in meaning)
'one's going to miss tracking european' is the wordplay.
'one' becomes 'i' (Roman numeral).
'going to' becomes 'll' (as in he'll, we'll etc).
'miss' becomes 'gal' (synonyms).
'tracking' means one lot of letters go next to another (track can mean to follow or go after).
'european' becomes 'E' (abbreviation e.g. EU).
'gal' put after 'e' is 'egal'.
'i'+'ll'+'egal'='ILLEGAL'
(Other definitions for illegal that I've seen before include "Ignoring certain acts" , "Unauthorised" , "Not lawful" , "murder sure is!" , "Black" .)