Great sign misspelling 'bumps (9)

'misspelling 'bumps' is the definition.
I can't judge whether this defines the answer.

'great sign' is the wordplay.
I cannot quite understand how this works, but
'great' could be 'swell' (synonyms) and 'swell' is located in the answer.
an anagram of 'sign' is 'ings' which is located in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?