Tanks in shade getting fresh air (7)
I believe the answer is:
'tanks' is the definition.
(aquarium is a kind of tank)
'shade getting fresh air' is the wordplay.
'shade' becomes 'aqua' (I've seen this before).
'getting' is an insertion indicator.
'fresh' indicates an anagram.
'air' anagrammed gives 'ari'.
'aqua' placed around 'ari' is 'AQUARIA'.
'in' is the link.
(Other definitions for aquaria that I've seen before include "display tanks" , "Tanks or buildings for fish" , "Transparent fish tanks" .)