One in public relations recalled summary (5)
I believe the answer is:
recap
'summary' is the definition.
(recap is a kind of summary)
'one in public relations recalled' is the wordplay.
'one' becomes 'ace' ('ace' can be a synonym of 'one').
'in' indicates putting letters inside.
'public relations' becomes 'pr'.
'recalled' says the letters should be written backwards.
'ace' inserted within 'pr' is 'pacer'.
'pacer' reversed gives 'RECAP'.
(Other definitions for recap that I've seen before include "Go over again with backward pacer" , "Go back over the main points" , "Final summary" , "look back on past things" , "Reiterate" .)