Garden structure by Olga, cleverly (7)
I believe the answer is:
pergola
'garden structure' is the definition.
(I've seen this before)
'by olga cleverly' is the wordplay.
'by' becomes 'per'.
'cleverly' indicates an anagram.
'olga' is an anagram of 'gola'.
'per'+'gola'='PERGOLA'
(Other definitions for pergola that I've seen before include "Arched garden structure" , "This'll support climbers" , "Lag rope (anag.)" , "Garden support" , "Garden trellis feature" .)