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' is a charade indicator (letters next to each other) (bottom letters provide a support for the top ones).
'suffering' indicates anagramming the letters.
'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".)