Force the Queen to release fanatic (7)
I believe the answer is:
fervent
'fanatic' is the definition.
'force the queen to release' is the wordplay.
'force' becomes 'f' (symbol used in Physics e.g. f=ma).
'the queen' becomes 'er' (Elizabeth Regina).
'to release' becomes 'vent'.
'f'+'er'+'vent'='FERVENT'
(Other definitions for fervent that I've seen before include "Hot" , "Enthusiastic" , "Zealous" , "Impassioned" , "Ardent" .)