Likely to snap under pressure (5)
'likely to snap' is the definition.
(I've seen this in another clue)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for testy that I've seen before include "Quick to anger" , "Easily annoyed" , "likely to flare up?" , "Captious" , "Irritably impatient" .)
'likely' is the definition.
Both the answer and definition are adjectives. Maybe you can see an association between them that I can't see?
'snap under pressure' is the wordplay.
I cannot really understand how this works, but
'under' could be 'per' (both can mean 'in accordance with') and 'per' is present in the answer.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for ill-tempered that I've seen before include "chippy" , "Irritable" .)