Find faults with film lecture (6)

I believe the answer is:

carpet

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'lecture' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'find faults with film' is the wordplay.
'find faults with' becomes 'carp' (I can't justify this - if you can you should believe this answer much more).
'film' becomes 'ET' (E.T. the Extra-Terrestrial).
'carp'+'et'='CARPET'

Can you help me to learn more?

(Other definitions for carpet that I've seen before include "Slate" , "Reprimand severely" , "Reprimand, reprove" , "Tear a strip off" , "Large rug" .)

I've seen this clue in The Sun and The Times.

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