Strong Greek holding shelves evenly (8)
I believe the answer is:
athletic
'strong' is the definition.
(I've seen this before)
'greek holding shelves evenly' is the wordplay.
'greek' becomes 'attic' (Attic is an example**).
'holding' is an insertion indicator.
'evenly' means one should take alternating letters (even-numbered letters only).
The alternating letters of 'shelves' are 'hle'.
'attic' placed around 'hle' is 'ATHLETIC'.
(Other definitions for athletic that I've seen before include "Strong and sporty" , "Fit and sporty" , "Active, sporty" , "Team" , "Given to partaking in sporting events" .)