Dear Rita, I misinterpreted X-ray (9)
I believe the answer is:
irradiate
'x-ray' is the definition.
(thesaurus)
'dear rita i misinterpreted' is the wordplay.
'misinterpreted' is an anagram indicator.
'dear'+'rita'+'i'='dearritai'
'dearritai' is an anagram of 'IRRADIATE'.
(Other definitions for irradiate that I've seen before include "Shine light on" , "Shed light on" , ""One fine day" would do" , "Make bright" .)