Crossword Genius

Printing unit to ply ego, sadly (8)

Ross

I believe the answer is:

logotype

I'm a little stuck... Click here to teach me more about this clue!

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

'to ply ego sadly' is the wordplay.
'sadly' is an anagram indicator.
'to'+'ply'+'ego'='toplyego'
'toplyego' anagrammed gives 'LOGOTYPE'.

Can you help me to learn more?

(Other definitions for logotype that I've seen before include "Printing block" , "time-saving device at printer's" , "Identifying symbol" .)

I've seen this clue in The Daily Express.
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