Address of old shop I must visit (7)
I believe the answer is:
oration
'address' is the definition.
(oration is a kind of address)
'old shop i must visit' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'shop' becomes 'rat' (I've seen this in other clues).
'i must visit' becomes 'ion' (I can't explain this - if you can you should believe this answer much more).
'o'+'rat'+'ion'='ORATION'
'of' is the link.
Can you help me to learn more?
(Other definitions for oration that I've seen before include "An eloquent speech" , "Type 16 [OF SPEECH]" , "Making a speech" , "A formal or public speech" , "eulogy" .)