One supports poor Bach suffering a fear of heights (10)
I believe the answer is:
acrophobia
'fear of heights' is the definition.
(I've seen this in another clue)
'one supports poor bach suffering a' is the wordplay.
'one' becomes 'i' (Roman numeral).
'supports' says to put letters next to each other (bottom letters provide a support for the top ones).
'suffering' indicates an anagram.
'poor'+'bach'='poorbach'
'poorbach' anagrammed gives 'acrophob'.
'i' put after 'acrophob' is 'acrophobi'.
'acrophobi'+'a'='ACROPHOBIA'
(Another definition for acrophobia that I've seen is " Arabic hoop (anag) - fear of heights".)