Drop it in opening of Dominican church (5)
I believe the answer is:
ditch
'drop' is the definition.
(I've seen this before)
'it in opening of dominican church' is the wordplay.
'in' means one lot of letters goes inside another.
'opening of' says to take the initial letters.
'church' becomes 'ch' (common abbreviation).
The first letter of 'dominican' is 'd'.
'd'+'ch'='dch'
'it' going inside 'dch' is 'DITCH'.
(Other definitions for ditch that I've seen before include "Jettison" , "Land in water" , "give up" , "long depression" , "side of field?" .)