Impractical chief who is concealed by mist (4,2,3,6)
I believe the answer is:
head in the clouds
'concealed by mist' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives sometimes define each other.
'impractical chief who' is the wordplay.
I cannot really understand how this works, but
'impractical' could be 'intheclouds' (I've seen this in another clue) and 'intheclouds' is found in the answer.
'chief' could be 'head' (synonyms) and 'head' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'is' acts as a link.
Can you help me to learn more?
(Other definitions for head in the clouds that I've seen before include "Boss, between 4 and 6 [NIMBUS & CUMULUS]" , "practically useless?" .)