Yell desperately on being locked inside, desolate (6)
I believe the answer is:
lonely
'desolate' is the definition.
(thesaurus)
'yell desperately on being locked' is the wordplay.
'desperately' indicates an anagram.
'on' indicates putting letters inside (as in clothing \'on\' a person).
'being locked' becomes 'on' (I can't justify this - if you can you should believe this answer much more).
'yell' is an anagram of 'lely'.
'lely' placed around 'on' is 'LONELY'.
'inside' is the link.
Can you help me to learn more?
(Other definitions for lonely that I've seen before include "Unfrequented" , "Unhappily unattached persons?" , "From the beginning (Latin)" , "Short of companionship" , "... in need of company ..." .)