Happy clearing last away (4)

I believe the answer is:

glad

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'happy' is the definition.
(I know that happy can be written as glad)

'clearing last away' is the wordplay.
'last' suggests the final letters.
'away' becomes 'lad' (I can't justify this - if you can you should give a lot more credence to this answer).
The last letter of 'clearing' is 'g'.
'g'+'lad'='GLAD'

Can you help me to learn more?

(Other definitions for glad that I've seen before include "More than willing" , "Happy, pleased" , "Contented" , "Elated" , "Informal flower < -girl" .)

I've seen this clue in The Telegraph.

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