It's fine to pass half an hour in composing tunes (7)
I believe the answer is:
tenuous
'it's fine' is the definition.
(synonyms)
'hour in composing tunes' is the wordplay.
'hour' becomes 'ou' (I am not sure about this - if you are sure you should believe this answer much more).
'in' indicates putting letters inside.
'composing' indicates anagramming the letters.
'tunes' with letters rearranged gives 'tenus'.
'ou' placed inside 'tenus' is 'TENUOUS'.
'to pass half an' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for tenuous that I've seen before include "Flimsy - uncertain" , "Thin - slight" , "Very thin in form, having little validity" , "Sketchy" , "Very slight (connection)" .)