Section of popular Gorecki composition (5)
I believe the answer is:
'composition' is the definition.
(I know that largo is a type of musical passage)
'section of popular gorecki' is the wordplay.
'section of' indicates the answer is hidden within the clue.
'LARGO' can be found hidden inside 'popular gorecki'.
(Other definitions for largo that I've seen before include "(Of music) broad and slow - Bond villain" , "taking it steady" , "at stately speed" , "Mus. slow movement" , "Moderately slowly" .)