Rent a seaside place on the Adriatic (5)
I believe the answer is:
split
'rent a seaside' is the definition.
'split' can be an answer for 'rent' (rent can mean split or torn). I am unsure of the 'a seaside' bit.
'place on the adriatic' is the wordplay.
'place' becomes 'pl' (abbreviation used in postal addresses).
'on' indicates putting letters inside.
'the adriatic' becomes 'sit' (I can't justify this - if you can you should give a lot more credence to this answer).
'pl' going into 'sit' is 'SPLIT'.
Can you help me to learn more?
(Other definitions for split that I've seen before include "Break forcibly" , "Chop or divide" , "See 18" , "Break in pieces - leave" , "shared by a couple?" .)