3: Many a retired thoroughbred
4: Experience a lack of oxygen, perhaps
7: Ending of many WWW addresses
12: Like the fabled piper
15: Hazarding a guess: doctor who puts stomach muscles in pulleys?
25: Reactions to fresh remarks, maybe
26: Like Schubert's music, e.g.
28: Himalayan monasteries
32: Revolutionary rebel Daniel
34: One's good name, briefly
44: Logic circuit element
54: Flute or saxophone variety
55: Mountain climber's challenge