Persuasive doctor to queen crossing line (8)
I believe the answer is:
eloquent
'persuasive' is the definition.
(I've seen this before)
'doctor to queen crossing line' is the wordplay.
'doctor' indicates anagramming the letters.
'crossing' indicates putting letters inside.
'line' becomes 'l'.
'to'+'queen'='toqueen'
'toqueen' is an anagram of 'eoquent'.
'eoquent' placed around 'l' is 'ELOQUENT'.
(Other definitions for eloquent that I've seen before include "Using language fluently and effectively" , "Forceful and persuasive in speech" , "Silver-tongued, articulate" , "Axilla; oxter" , "Persuasive, as a speaker" .)