Frequently seen within solid walls: carpet and pot? (4,4)

'pot?' is the definition.
(pot is a kind of soft drug)

'frequently seen within solid walls carpet' is the wordplay.
'frequently' becomes 'oft' (oft can mean frequently, eg oft-quoted).
'seen within' is an insertion indicator.
'walls' suggests removing the centre (the walls are the letters on each edge).
'carpet' becomes 'rug' (synonyms).
'solid' with its centre removed is 'sd'.
'oft' put inside 'sd' is 'softd'.
'softd'+'rug'='SOFT DRUG'

'and' is the link.