Tyne cop's remarkable power (7)
I believe the answer is:
potency
'power' is the definition.
('potency' can be a synonym of 'power')
'tyne cop's remarkable' is the wordplay.
'remarkable' indicates an anagram.
'tyne'+'cop'='tynecop'
'tynecop' anagrammed gives 'POTENCY'.
(Other definitions for potency that I've seen before include "Might" , "Power; pet cony (anag.)" , "Great power" , "Capacity" , "Strength - effectiveness" .)