Unclear how unfortunate cubs got covered in mineral (7)
I believe the answer is:
obscure
'unclear' is the definition.
(I've seen this before)
'unfortunate cubs got covered in mineral' is the wordplay.
I cannot really see how this works, but
an anagram of 'cubs' is 'bscu' which is located in the answer.
'mineral' could be 'ore' (ore is a kind of mineral) and 'ore' is present in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
'how' is the link.
Can you help me to learn more?
(Other definitions for obscure that I've seen before include "Hazy or cryptic" , "Uncertain; indistinct" , "Unclear - recondite" , "Like Jude, not well known" , "Cloudy or indistinct" .)