Afflicted by rickets, misshapen bones, essentially (8)
I believe the answer is:
stricken
'afflicted' is the definition.
(synonyms)
'rickets misshapen bones essentially' is the wordplay.
'misshapen' indicates anagramming the letters.
'essentially' says to take the centre.
The middle letter of 'bones' is 'n'.
'rickets' with letters rearranged gives 'stricke'.
'stricke'+'n'='STRICKEN'
'by' acts as a link.
(Other definitions for stricken that I've seen before include "Affected by illness or grief - like a blow?" , "Seriously affected (by, eg, condition)" , "Laid low, out of action" , "Word that can be appended to both 1 and 2 down" , "Seriously afflicted" .)