Sits reel out though unwearied (8)
I believe the answer is:
tireless
'unwearied' is the definition.
(thesaurus)
'sits reel out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'sits'+'reel'='sitsreel'
'sitsreel' anagrammed gives 'TIRELESS'.
'though' is the link.
(Other definitions for tireless that I've seen before include "Permanently lively" , "Having great energy" , "Full of energy" , "Never wearying" , "Having inexhaustible energy" .)