Humiliated adolescent initially remains in bed (7)
I believe the answer is:
abashed
'humiliated' is the definition.
(thesaurus)
'adolescent initially remains in bed' is the wordplay.
'initially' suggests taking the first letters.
'remains' becomes 'ash' (remains of a fire).
'in' indicates putting letters inside.
The initial letter of 'adolescent' is 'a'.
'ash' inserted within 'bed' is 'bashed'.
'a'+'bashed'='ABASHED'
(Other definitions for abashed that I've seen before include "floored" , "Shamefaced" , "Feeling uneasy" , "Embarrassed or ashamed" , "Embarrassed or discomfited" .)