Fastened outside again, in rows (6)
I believe the answer is:
tiered
'in rows' is the definition.
(laid out in tiers or rows)
'fastened outside again' is the wordplay.
'fastened' becomes 'tied' (tying is a kind of fastening).
'outside' indicates putting letters inside (some letters go outside others).
'again' becomes 're' (prefix meaning 'again').
'tied' going around 're' is 'TIERED'.
(Other definitions for tiered that I've seen before include "Cunstructed in layers" , "Constructed in layers, like wedding cake" , "Ranked" , "Arranged in rising 5 ac" , "Laid out in layers, like wedding cake" .)