Harbour deal adjusted in stalemate (8)
I believe the answer is:
deadlock
'stalemate' is the definition.
(synonyms)
'harbour deal adjusted in' is the wordplay.
'harbour' becomes 'dock' (I've seen this before).
'adjusted' indicates anagramming the letters.
'in' is an insertion indicator.
'deal' with letters rearranged gives 'eadl'.
'dock' placed around 'eadl' is 'DEADLOCK'.
(Other definitions for deadlock that I've seen before include "Intractable problem" , "tie" , "Impasse, standoff" , "Stalemate - it requires a key to open" , "Log jam" .)