Modern gallery in quiet centre (5,2,3,3)
I believe the answer is:
state of the art
'modern' is the definition.
('state-of-the-art' can be similar in meaning to 'modern')
'gallery in quiet centre' is the wordplay.
'gallery' becomes 'tate' (I've seen this before).
'in' means one lot of letters goes inside another.
'quiet' becomes 'soft' ('soft' can be similar in meaning to 'quiet'**).
'centre' becomes 'heart' ('heart' can be a synonym of 'centre').
'tate' placed inside 'soft' is 'stateoft'.
'stateoft'+'heart'='STATE-OF-THE-ART'
(Other definitions for state of the art that I've seen before include "Highest level of development at a particular time" , "Latest developments" , "Modern" , "Technologically most recent" , "responsibility of picture restorers" .)