Composition by an Italian poet (7)
I believe the answer is:
andante
'composition' is the definition.
'by an italian poet' is the wordplay.
'by' means one lot of letters go next to another.
'italian poet' becomes 'dante' (I've seen this before).
'an' put next to 'dante' is 'ANDANTE'.
(Other definitions for andante that I've seen before include "Musically, in moderately slow time" , "progressing slowly" , "Moderately slow piece of music" , "For players, rather slow" , "(Musically) at a moderate pace" .)