Harbour oddly deep and steep (8)
I believe the answer is:
marinade
'steep' is the definition.
(marinading is a kind of steeping)
'harbour oddly deep' is the wordplay.
'harbour' becomes 'marina' (I've seen this before).
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
The alternate letters of 'deep' are 'de'.
'marina'+'de'='MARINADE'
'and' is the link.
(Other definitions for marinade that I've seen before include "Mixture for soaking meat before cooking" , "Soak food before cooking" , "spicy sauce" , "In a dream (anag.)" , "pickle" .)