Artist seen in behind first of several wall hangings (7)

'wall hangings' is the definition.
(arras is a kind of wall hanging)

'artist seen in behind first of several' is the wordplay.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'seen in' is an insertion indicator.
'behind' becomes 'arse' ('arse' can be a synonym of 'behind'**).
'first of' suggests taking the first letters.
The initial letter of 'several' is 's'.
'ra' put into 'arse' is 'arrase'.
'arrase'+'s'='ARRASES'