Brown has seized her working capital (6)
I believe the answer is:
tehran
'capital' is the definition.
(capital of Iran)
'brown has seized her working' is the wordplay.
I cannot really understand how this works, but
an anagram of 'her' is 'ehr' which is within the answer.
'brown' could be 'tan' (tan is a kind of brown) and 'tan' is located in the remaining letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tehran that I've seen before include "Iranian capital" , "Iran's capital" , "Capital city of Iran (6)" .)