Infant, tiny, unclothed? That's appalling! (7)

I believe the answer is:

abysmal

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

'appalling' is the definition.
(abysmal can mean terrible)

I don't understand the rest of the clue.

(Other definitions for abysmal that I've seen before include "Very bad, poor" , "Very bad indeed" , "Extremely bad, appalling" , "Deplorable, extremely bad - say ignorance" , "Immeasurably bad" .)

I've seen this clue in The Times.

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