Duchamp's first on a platform, initially talking shop with Hans Arp, Man Ray et al. (8)

'hans arp man ray et al' is the definition.

'duchamp's first on a platform initially talking shop' is the wordplay.
'first' suggests taking the first letters.
'on' means one lot of letters go next to another.
'platform' becomes 'dais' (dais is a kind of platform**).
'initially' suggests taking the first letters.
The first letter of 'duchamp' is 'd'.
The first letters of 'talking shop' is 'ts'.
'd'+'a'+'dais'+'ts'='DADAISTS'

'with' is the link.