Haughty old heroine’s song composed about husbands (2,4,4,5)
I believe the answer is:
on ones high horse
'haughty' is the definition.
(someone on their high horse is haughty or vain)
'old heroine's song composed about husbands' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'composed' indicates anagramming the letters.
'about' is an insertion indicator.
'husbands' becomes 'hh' (an abbreviation for husband written twice).
'o'+'heroines'+'song'='oheroinessong'
'oheroinessong' with letters rearranged gives 'ononeshigorse'.
'ononeshigorse' going around 'hh' is 'ON ONES HIGH HORSE'.
(Other definitions for on ones high horse that I've seen before include "Overbearing" , "like George IV in Trafalgar Square?" , "With an air of superiority" , "in an attitude of smug superiority" .)