Gosh! Harbour's invaded by Spain (7)
I believe the answer is:
heavens
'gosh' is the definition.
(interjections!)
'harbour's invaded by spain' is the wordplay.
'harbour's' becomes 'haven's' ('haven' can be a synonym of 'harbour').
'invaded by' is an insertion indicator.
'spain' becomes 'e' (abbreviation for Espana).
'havens' going around 'e' is 'HEAVENS'.
(Other definitions for heavens that I've seen before include "Gosh!" , "Places of supreme happiness" , "Firmament, celestial sphere" , "the blue" , "Expression of surprise" .)