Daughter abandons flirtation for marriage (8)
I believe the answer is:
alliance
'for marriage' is the definition.
(I've seen this before)
'daughter abandons flirtation' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'abandons' indicates named letters should be taken away.
'flirtation' becomes 'dalliance' (both can mean a casual relationship).
'dalliance' with 'd' taken away is 'ALLIANCE'.
(Other definitions for alliance that I've seen before include "Coalition or union" , "Association for mutual benefit" , "Union for mutual benefit" , "League - treaty" , "Kind of partnership with canaille" .)