Law set by head of administration in province of 1D (5)
I believe the answer is:
judea
'province of 1d' is the definition.
I can't tell whether this defines the answer.
'law set by head of administration' is the wordplay.
'law' becomes 'Jude' (actor Jude Law).
'set by' means one lot of letters go next to another.
'head of' indicates taking the first letters.
The first letter of 'administration' is 'a'.
'jude'+'a'='JUDEA'
'in' is the link.
Can you help me to learn more?
(Other definitions for judea that I've seen before include "Biblical land" , "where 6a [JESUS] lived" .)