Be trapped in large bedroom by an alert dog (8)
I believe the answer is:
doberman
'alert dog' is the definition.
'doberman' can be an answer for 'dog' (breed of dog). I'm not certain of the 'alert' bit.
'be trapped in large bedroom by an' is the wordplay.
'trapped in' is an insertion indicator.
'large bedroom' becomes 'dorm' (I have seen 'Communal bedroom ' mean 'dorm' so perhaps 'bedroom' could also mean 'dorm'. I am not sure about the 'large' bit.).
'by' says to put letters next to each other.
'be' placed inside 'dorm' is 'doberm'.
'doberm'+'an'='DOBERMAN'
Can you help me to learn more?
(Other definitions for doberman that I've seen before include "Dog used as guard - bond mare (anag)" , "...pinscher, large dog" , "Big dog" , "Long-legged terrier" , "Thematic type [DOG]" .)