Is prepared to stand by the English woman (6)

'woman' is the definition.

'is prepared to stand by the english' is the wordplay.
'prepared' becomes 'set' (set up or ready).
'to stand' shows that the letters should be reversed in order (I've seen 'standing' mean this (in a down clue, letters stand up)).
'by' is a charade indicator (letters next to each other).
'the english' becomes 'E' (abbreviation as in OED).
'is'+'set'='isset'
'isset' back-to-front is 'tessi'.
'tessi'+'e'='TESSIE'