Worried about grasping unknown ancient language (5)

I believe the answer is:

aztec

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

'ancient language' is the definition.
'Aztec' can be an answer for 'language' (language of the Aztec Empire). I am unsure of the 'ancient' bit.

'worried about grasping unknown' is the wordplay.
'worried' becomes 'ate' (something worrying may eat someone up).
'about' becomes 'c' (abbreviation for 'circa').
'grasping' indicates putting letters inside.
'unknown' becomes 'z' (algebra).
'ate'+'c'='atec'
'atec' placed around 'z' is 'AZTEC'.

Can you help me to learn more?

(Other definitions for aztec that I've seen before include "Like Montezuma?" , "Pre-conquest Mexican Indian" , "Pre-Spanish Mexican" , "old American" , "American people" .)

I've seen this clue in The Times.

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