Memo about bodyguard (8)
I believe the answer is:
reminder
'memo' is the definition.
(I've seen this in another clue)
'about bodyguard' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'bodyguard' becomes 'minder' (minder can mean a bodyguard).
're'+'minder'='REMINDER'
(Other definitions for reminder that I've seen before include "Memento" , "Memory-jogger" , "Knot in handkerchief?" , "Memory refresher" , "note" .)