Stuck-up old Stockholm-born actress failing to finish show off (4)
I believe the answer is:
brag
'show off' is the definition.
(both can mean to boast about something)
'stuck-up old stockholm-born actress failing to finish' is the wordplay.
I cannot really see how this works, but
'born' could be 'b' (abbreviation next to the year of someone's birth) and 'b' is found in the answer.
The remaining letters 'rag' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for brag that I've seen before include "game of bluff" , "Blow one's own trumpet" , "'Show off, boast (4)'" , "Boast about garb" , "Boast ? card-game" .)