Croatian port increased part (5,2)
I believe the answer is:
split up
'part' is the definition.
(I know that part can be written as split up)
'croatian port increased' is the wordplay.
'croatian port' becomes 'split' (I've seen this before).
'increased' becomes 'up' (something that's up has increased or risen).
'split'+'up'='SPLIT UP'
(Other definitions for split up that I've seen before include "Part company" , "Separate" , "Take apart" , "Divorce" , "Parted company" .)