Lie in wait possibly? We must be concealed first (7)
I believe the answer is:
initial
'first' is the definition.
(similar in meaning)
'lie in wait possibly? we must be concealed' is the wordplay.
I cannot really see how this works, but
'in' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for initial that I've seen before include "Beginning - first letter" , "Primary" , "Name's first letter" , "Start of name" , "Original; beginning" .)