This clip appears in It Came From Hollywood, as part of a montage of scenes of women being attacked by mobile brains. That was, I suppose, a trope in low-budget mid-20th-century horror/sci fi films.
The specific movie depicted may be Fiend Without A Face.
This intelligence soon begins to multiply its numbers by claiming even
more local victims. These creatures later become visible while
continuing to feed on the higher levels of power now being generated
at the airbase. Their mutated "bodies" are revealed to be the missing,
now enlarged brains and connected spinal cords removed from their
victims; the spinal cords have become very flexible and have sprouted
feelers. These mutations allow the creatures to move quickly and even
to leap; each brain has also developed a pair of small eyes on
extended eye stalks.
The film climaxes with the visible creatures
attacking an isolated house where most of the film's main characters
have gathered to discuss the growing crisis. Having come armed, the
defenders discover the creatures can be easily dispatched with
well-aimed gun shots to their exposed brain-bodies.