Sanction representative, old, visiting the jug (7)
I believe the answer is:
empower
'sanction' is the definition.
(sanction can mean to empower or permit)
'representative old visiting the jug' is the wordplay.
'representative' becomes 'mp' (Member of Parliament, a representative).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'visiting' indicates putting letters inside.
'the jug' becomes 'ewer' (type of vessel).
'mp'+'o'='mpo'
'mpo' inserted inside 'ewer' is 'EMPOWER'.
(Other definitions for empower that I've seen before include "Give authority to, enable" , "Give authority to, authorise" , "Entitle" , "Authorize" , "Authorise, endue" .)