Very Liberal women labouring to secure victory promise (6,3)

'promise' is the definition.
(I know that Solemn vow is a type of religious vows)

'very liberal women labouring to secure victory' is the wordplay.
'very' becomes 'so' (both can mean 'extremely').
'liberal' becomes 'l' (abbreviation).
'labouring' indicates an anagram (letters worked or laboured into a new form).
'to secure' means one lot of letters goes inside another (inserted letters are secured inside).
'victory' becomes 'v'.
'women' anagrammed gives 'emnow'.
'emnow' placed around 'v' is 'emnvow'.
'so'+'l'+'emnvow'='SOLEMN VOW'