Minute lid turned out to be boundless (9)
I believe the answer is:
unlimited
'to be boundless' is the definition.
(I've seen this before)
'minute lid turned' is the wordplay.
'turned' indicates anagramming the letters.
'minute'+'lid'='minutelid'
'minutelid' is an anagram of 'UNLIMITED'.
'out' acts as a link.
(Other definitions for unlimited that I've seen before include "Boundless" , "out of bounds" .)