Record acting leader left behind (5)
I believe the answer is:
album
'record' is the definition.
(I've seen this before)
'acting leader left behind' is the wordplay.
'acting' becomes 'a' (abbreviation, eg in job titles).
'leader' indicates taking the first letters.
'behind' becomes 'bum' (synonyms).
The initial letter of 'left' is 'l'.
'a'+'l'+'bum'='ALBUM'
(Other definitions for album that I've seen before include "Book for stamps/photos" , "(Photograph) book" , "Music record or photo book" , "Cuttings book" , "Book of collections" .)