Presto's opposite (5)
I believe the answer is:
lento
'presto's opposite' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lento that I've seen before include "It's slower than adagio" , "Old sayings" , "Slow (music)" , "Slow (mus.)" , "Instruction to players" .)