Tanks in piazza stripped, one occupying area after evacuation (7)

'tanks' is the definition.
(aquarium is a kind of tank)

'piazza stripped one occupying area after evacuation' is the wordplay.
'piazza' becomes 'square' (synonyms).
'stripped' indicates the central letters (outside letters removed).
'one occupying' is an insertion indicator (inserted letters occupy or enter the word).
'area' becomes 'a' (maths abbreviation).
'after evacuation' becomes 'ia' (I can't justify this - if you can you should give a lot more credence to this answer).
The central letters of 'square' are 'quar'.
'a'+'ia'='aia'
'quar' put within 'aia' is 'AQUARIA'.

'in' is the link.

Can you help me to learn more?