Pictures came in reels (6)
I believe the answer is:
cinema
'pictures' is the definition.
(I've seen this in another clue)
'came in reels' is the wordplay.
'reels' is an anagram indicator (letters dance or reel around).
'came'+'in'='camein'
'camein' is an anagram of 'CINEMA'.
(Other definitions for cinema that I've seen before include "(Building for) the movies" , "Filmdom" , "Picture house" , "Motion pictures" , "Screening" .)