False star explodes in middle of freeze-up (6)

I believe the answer is:

ersatz

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'false' is the definition.
(I've seen this before)

'star explodes in middle of freeze-up' is the wordplay.
'explodes' indicates an anagram.
'in middle of' is an insertion indicator.
'freeze' becomes 'ze' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'ze' reversed gives 'ez'.
'star' anagrammed gives 'rsat'.
'rsat' inserted into 'ez' is 'ERSATZ'.

Can you help me to learn more?

(Other definitions for ersatz that I've seen before include "Mock" , "Artificial, imitation - from German" , "Inferior substitute" , "Imitation (from Ger.)" , "Not real or genuine" .)

I've seen this clue in The Times.

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