Woman’s with copper, thin, very powerful (9)
I believe the answer is:
herculean
'powerful' is the definition.
(powerful like Hercules)
'woman's with copper thin' is the wordplay.
'woman's' becomes 'her' (belonging to a woman).
'with' is a charade indicator (letters next to each other).
'copper' becomes 'Cu' (Cu is the chemical symbol for copper).
'thin' becomes 'lean' (synonyms).
'her'+'cu'+'lean'='HERCULEAN'
'very' acts as a link.
(Other definitions for herculean that I've seen before include "Requiring very great effort" , "Old Labour" , "Enormously demanding (task)" , "Powerful" , "So enormous a task" .)