Crossword Genius

Took the test again after returning a shocker (5)

Ross

I believe the answer is:

taser

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

'a shocker' is the definition.
(something which gives electric shocks)

'took the test again after returning' is the wordplay.
'took the test' becomes 'tas' (I can't explain this - if you can you should believe this answer much more).
'again' becomes 're' (prefix meaning 'again').
'after returning' says the letters should be written backwards.
're' back-to-front is 'er'.
'tas'+'er'='TASER'

Can you help me to learn more?

(Other definitions for taser that I've seen before include "The weapon delivers a temporary paralysing electric shock" , "Device used to stun someone temporarily" , "A temporary stunner?" , "Shocking device used by the police?" , "PC kit" .)

I've seen this clue in The Guardian.
Want a hint initially instead of a full solution? Install my app