Present king keen on old fascist guards (9)
I believe the answer is:
introduce
'present' is the definition.
(I know that present can be written as introduce)
'king keen on old fascist guards' is the wordplay.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'keen on' becomes 'into' (I've seen this in other clues).
'old fascist' becomes 'duce' (Benito Mussolini was called Il Duce).
'guards' means one lot of letters goes inside another (inserted letters are guarded).
'into'+'duce'='intoduce'
'r' placed into 'intoduce' is 'INTRODUCE'.
(Other definitions for introduce that I've seen before include "Present, make known" , "Make known to by way of reduction" , "Usher in" , "Bring in - cause to meet" , "Bring in for the first time" .)