Sacred time's filled with passion (5)
I believe the answer is:
hotly
'with passion' is the definition.
(I've seen this before)
'sacred time's filled' is the wordplay.
'sacred' becomes 'holy' (similar in meaning).
'time' becomes 't'.
'filled' means one lot of letters goes inside another.
'holy' placed around 't' is 'HOTLY'.
(Other definitions for hotly that I've seen before include "With zeal - as one may be pursued" , "in an ardent manner" , "showing passion" , "disputed thus?" , "Heatedly" .)