Dreadful ulcer is more than one can bear (5)

I believe the answer is:

cruel

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

'more than one can bear' is the definition.
I can't judge whether this defines the answer.

'dreadful ulcer' is the wordplay.
'dreadful' indicates an anagram.
'ulcer' is an anagram of 'CRUEL'.

'is' acts as a link.

Can you help me to learn more?

(Other definitions for cruel that I've seen before include "Merciless" , "Callous" , "Lucre (anag.)" , "Sadistic, causing suffering" , "Diabolical" .)

I've seen this clue in the Irish Times.

Want a hint initially instead of a full solution? Install my app