Yours truly trapped by angry servant (4)
I believe the answer is:
maid
'servant' is the definition.
(maid is a kind of servant)
'yours truly trapped by angry' is the wordplay.
'yours truly' becomes 'i'.
'trapped by' means one lot of letters goes inside another.
'angry' becomes 'mad' (similar in meaning).
'i' put inside 'mad' is 'MAID'.
(Other definitions for maid that I've seen before include "Damsel" , "One in service" , "employee" , "daughter?" , "Female servant - young girl" .)