Mud around gallery took new form (7)
I believe the answer is:
mutated
'took new form' is the definition.
The definition and answer can be both related to change as well as being past participle verbs.
Maybe you can see a link between them that I don't see?
'mud around gallery' is the wordplay.
'around' means one lot of letters goes inside another.
'gallery' becomes 'tate' (Tate Modern, Tate Britain etc).
'mud' placed around 'tate' is 'MUTATED'.
Can you help me to learn more?
(Other definitions for mutated that I've seen before include "Changed form" , "made changes" , "Changed (biologically)" , "Made different" .)