Passage of old ship entering cold belt (8)
I believe the answer is:
crossing
'passage' is the definition.
(I've seen this before)
'old ship entering cold belt' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'ship' becomes 'ss'.
'entering' indicates putting letters inside.
'cold' becomes 'c' (eg on taps).
'belt' becomes 'ring'.
'o'+'ss'='oss'
'c'+'ring'='cring'
'oss' inserted inside 'cring' is 'CROSSING'.
'of' acts as a link.
(Other definitions for crossing that I've seen before include "Passage" , "Traversing" , "Junction" , "Journey over water" , "Where to go to the other side of the road" .)