Free cinema popcorn - initially consumed for free (10)
'free' is the definition.
'free cinema popcorn initially consumed' is the wordplay.
'free' indicates an anagram.
'initially' indicates taking the first letters.
'consumed' becomes 'ate' (eating is a kind of consuming).
The initial letter of 'popcorn' is 'p'.
'cinema' with letters rearranged gives 'emanci'.
'for' is the link.
(Other definitions for emancipate that I've seen before include "setting free", "Set free", "Free from slavery", "Liberate", "release".)