Speak to head of department during a shift (7)
I believe the answer is:
address
'speak to' is the definition.
(synonyms)
'head of department during a shift' is the wordplay.
'head of' suggests taking the first letters.
'during' is an insertion indicator.
'shift' becomes 'dress' (I've seen this before).
The initial letter of 'department' is 'd'.
'a'+'dress'='adress'
'd' inserted inside 'adress' is 'ADDRESS'.
(Other definitions for address that I've seen before include "Think about" , "Speak to the residence" , "Place of abode" , "directions in window" , "prepare for post" .)