Head of department in a frock making speech (7)
I believe the answer is:
address
'speech' is the definition.
(synonyms)
'head of department in a frock' is the wordplay.
'head of' indicates taking the first letters.
'in' indicates putting letters inside.
'frock' becomes 'dress' (synonyms).
The initial letter of 'department' is 'd'.
'a'+'dress'='adress'
'd' put within 'adress' is 'ADDRESS'.
'making' is the link.
(Other definitions for address that I've seen before include "personal details" , "Place of abode" , "Art" , "Speak to the residence" , "hail maybe?" .)