Quirky duo I left in part of sports arena? (8)
I believe the answer is:
outfield
'part of sports arena?' is the definition.
(outfield is part of a baseball pitch)
'quirky duo i left' is the wordplay.
'quirky' indicates an anagram.
'duo'+'i'+'left'='duoileft'
'duoileft' with letters rearranged gives 'OUTFIELD'.
'in' acts as a link.
(Other definitions for outfield that I've seen before include "Area away from the wicket" , "Part of pitch furthest from wicket" , "Area furthest from the stumps" , "Distant region of cricket ground" .)