Declaration of occupation (10)
I believe the answer is:
profession
This clue is a double definition.
'declaration' is the first definition.
(I've seen this before)
'occupation' is the second definition.
(profession is a kind of occupation)
'of' is the link.
(Other definitions for profession that I've seen before include "Occupation; declaration (of belief)" , "statement" , "career?" , "announcement" , "Job" .)