Woman in bed with touch of arthritis (6)
I believe the answer is:
bertha
'woman' is the definition.
'bed with touch of arthritis' is the wordplay.
'bed' becomes 'berth' (berth is a kind of bed).
'with' is a charade indicator (letters next to each other).
'touch of' indicates taking the first letters.
The first letter of 'arthritis' is 'a'.
'berth'+'a'='BERTHA'
'in' acts as a link.
(Other definitions for bertha that I've seen before include "Big - - , WW1 gun" , "Breath (anag) - girl's name" , "Woman's name" , "Girl's name - big German WWI gun" , "43-ton German howitzer, Big _____" .)