Speak to daughter wearing a formal garment (7)
I believe the answer is:
address
'speak to' is the definition.
(synonyms)
'daughter wearing a formal garment' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'wearing' means one lot of letters goes inside another.
'formal garment' becomes 'dress' (dress is a kind of garment. I am not sure about the 'formal' bit.).
'a'+'dress'='adress'
'd' put inside 'adress' is 'ADDRESS'.
Can you help me to learn more?
(Other definitions for address that I've seen before include "Where you live" , "Speak to at home?" , "directions in window" , "Direct words at" , "In almost desperate straits" .)