Strange-looking creature concealed itself, covered in nasty acne (7)
I believe the answer is:
echidna
'strange-looking creature concealed itself' is the definition.
I can't judge whether this definition defines the answer.
'covered in nasty acne' is the wordplay.
'covered' becomes 'hid' (I've seen this in another clue).
'in' is an insertion indicator.
'nasty' is an anagram indicator (a nasty or wrong spelling).
'acne' with letters rearranged gives 'ecna'.
'hid' going inside 'ecna' is 'ECHIDNA'.
Can you help me to learn more?
(Other definitions for echidna that I've seen before include "Such a beast" , "Had nice (anag) -- spiny anteater" , "Spiny Aus. mammal" , "This insectivore" , "Australian creature" .)