Fashionable pen starts to leak ink, staining hand (7)
I believe the answer is:
stylish
'fashionable' is the definition.
(I know that fashionable can be written as stylish)
'pen starts to leak ink staining hand' is the wordplay.
'pen' becomes 'sty' (both can mean an animal enclosure).
'starts to' says to take the initial letters.
The first letters of 'leak ink staining hand' is 'lish'.
'sty'+'lish'='STYLISH'
(Other definitions for stylish that I've seen before include "Soigne" , "Having elegant taste" , "Fashionably elegant" , "Fashionable, elegant" , "Trendy" .)