Get to deliver a sermon when leader is absent (5)
I believe the answer is:
reach
'get to' is the definition.
(synonyms)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for reach that I've seen before include "Come up to - stretch between bends" , "Arrive at; extend to" , "Grasp" , "Come to - stretch of river" , "Get to < throw up in the old" .)