Modern gallery shrouded in gentle compassion (5,2,3,3)
I believe the answer is:
state of the art
'modern' is the definition.
(similar in meaning)
'gallery shrouded in gentle compassion' is the wordplay.
'gallery' becomes 'tate' (Tate Modern, Tate Britain etc).
'shrouded in' indicates putting letters inside.
'gentle' becomes 'soft' (similar in meaning).
'compassion' becomes 'heart' (I've seen this before).
'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" , "Incorporating the newest ideas and features" , "Technologically most recent" , "Highest level of development at the present time" , "concern of museum conservationist?" .)