Possibly, lewd queen worried doctor (10)
I believe the answer is:
adulterate
'doctor' is the definition.
(synonyms)
'possibly lewd queen worried' is the wordplay.
'possibly lewd' becomes 'adult' (as in adult humour).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'worried' becomes 'ate' (something worrying may eat someone up).
'adult'+'er'+'ate'='ADULTERATE'
(Other definitions for adulterate that I've seen before include "Make poorer by adding another substance" , "cut" , "Spike" , "Make impure by addition" , "Contaminate" .)