Fashionable pen is in left hand (7)
I believe the answer is:
stylish
'fashionable' is the definition.
(I know that fashionable can be written as stylish)
'pen is in left hand' is the wordplay.
'pen' becomes 'sty' (both can mean an animal enclosure).
'in' indicates putting letters inside.
'left hand' becomes 'lh' (this might be a standard abbreviation which I don't know about).
'is' placed into 'lh' is 'lish'.
'sty'+'lish'='STYLISH'
Can you help me to learn more?
(Other definitions for stylish that I've seen before include "Smart - attractively competent" , "Having elegant taste" , "Fashionably elegant" , "Imposingly smart" , "Fashionable, elegant" .)