Stroke ball around big, uncovered part of garden (5)
I believe the answer is:
patio
'part of garden' is the definition.
('patio' is part of 'garden')
'stroke ball around big uncovered' is the wordplay.
'stroke' becomes 'pat' (pat can mean to stroke or touch).
'ball' becomes 'o' (O looks like a ball).
'around' is an insertion indicator.
'uncovered' indicates the central letters.
The middle of 'big' is 'i'.
'pat'+'o'='pato'
'pato' placed around 'i' is 'PATIO'.
(Other definitions for patio that I've seen before include "Paved area next to house" , "Where to put barbecue" , "Inner courtyard" , "Spanish courtyard" , "Paved eating area adjoining house" .)