What our theme is all about sounds beautiful (4)
I believe the answer is:
fare
'what our theme is all' is the definition.
I can't tell whether this defines the answer.
'sounds beautiful' is the wordplay.
'sounds' shows a homophone (sound like).
'beautiful' becomes 'fair' (similar in meaning).
'fair' is a homophone of 'FARE'.
'about' is the link.
Can you help me to learn more?
(Other definitions for fare that I've seen before include "Taxi charge; food" , "Get on - passenger - provisions" , "what the commuter will pay" , "Amount charged" , "(Person paying) price for travel" .)