Married in August a female relative (7)
I believe the answer is:
grandma
'female relative' is the definition.
(I've seen this before)
'married in august a' is the wordplay.
'married' becomes 'm' (abbreviation, e.g. in genealogy).
'in' means one lot of letters goes inside another.
'august' becomes 'grand' (synonyms).
'grand'+'a'='granda'
'm' placed within 'granda' is 'GRANDMA'.
(Other definitions for grandma that I've seen before include "Parent's mother" , "St Winifred's School Choir sang about her" , "family member" , "Drag man to his relative" , "Darn, Mag is older relation" .)