Found in Tallinn, exhausted (3,2)
I believe the answer is:
all in
'exhausted' is the definition.
('all in' can mean exhausted)
'found in tallinn' is the wordplay.
'found in' indicates a hidden word.
'ALL-IN' can be found hidden inside 'tallinn'.
(Other definitions for all in that I've seen before include "expenses and costs included" , "Quite exhausted - everyone at home" , "without unexpected cost" , "Including everything" , "Inclusive; tired" .)