Filmed report showing gatecrashers finally invading recent dance (8)
I believe the answer is:
newsreel
'filmed report' is the definition.
(I've seen this before)
'gatecrashers finally invading recent dance' is the wordplay.
'finally' says to take the final letters.
'invading' indicates putting letters inside.
'recent' becomes 'new' (similar in meaning).
'dance' becomes 'reel' (reel is a kind of dance).
The final letter of 'gatecrashers' is 's'.
'new'+'reel'='newreel'
's' inserted into 'newreel' is 'NEWSREEL'.
'showing' is the link.
(Other definitions for newsreel that I've seen before include "Film report" , "Short film of current events" , "information screened" , "current events programme" , "Short current affairs cinema film" .)