One's blown a thousand going around park (5)
I believe the answer is:
kazoo
'one's blown' is the definition.
I can't judge whether this definition defines the answer.
'a thousand going around park' is the wordplay.
'thousand' becomes 'k' (synonyms).
'going around' says the letters should be written in reverse.
'park' becomes 'zoo' (I've seen this before).
'a'+'k'='ak'
'ak' back-to-front is 'ka'.
'ka'+'zoo'='KAZOO'
Can you help me to learn more?
(Other definitions for kazoo that I've seen before include "Simple musical instrument" , "Toy-like instrument into which one hums" , "Toy wind instrument that buzzes" , "Humming toy" .)