The odd ball is so-so compared with cloud nine (5)
I believe the answer is:
bliss
'cloud nine' is the definition.
(I've seen this before)
'the odd ball is so-so' is the wordplay.
'the odd' means one should take alternating letters.
'ball'+'is'+'so'+'so'='ballissoso'
The alternate letters of 'ballissoso' are 'BLISS'.
'compared with' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for bliss that I've seen before include "One who scored" , "Beatitude" , "rhapsody?" , "of composing?" , "'Where ignorance is ....., 'tis folly to be wise'" .)