Picture of harbour and rodent holding one (8)
I believe the answer is:
portrait
'picture' is the definition.
(portrait is a type of picture)
'harbour and rodent holding one' is the wordplay.
'harbour' becomes 'port' (I've seen this before).
'and' is a charade indicator (letters next to each other).
'rodent' becomes 'rat' (rat is a kind of rodent).
'holding' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'rat' going around 'i' is 'rait'.
'port'+'rait'='PORTRAIT'
'of' is the link.
(Other definitions for portrait that I've seen before include "Painting of a real person" , "characteristic depiction" , "Painted likeness of a person" , "Depiction of person" , "Person's picture" .)