Crossword Genius

Why the last two letters are convenient (5)

Ross

I believe the answer is:

handy

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

'convenient' is the definition.
(synonyms)

'why the last two letters' is the wordplay.
I cannot really see how this works, but
'why' could be 'y' and 'y' is found in the answer.
The remaining letters 'hand' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

'are' acts as a link.

Can you help me to learn more?

(Other definitions for handy that I've seen before include "Accessible" , "quite useful" , "Local - nearby" , "Near; useful" , "Useful and convenient" .)

I've seen this clue in The Globe and Mail.
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