First man to encounter a barrier (4)
I believe the answer is:
adam
'first man' is the definition.
(first man in the Bible)
'a barrier' is the wordplay.
'barrier' becomes 'dam' (dam is a kind of barrier).
'a'+'dam'='ADAM'
'to encounter' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for adam that I've seen before include "Fellow" , "Eden man" , "The first known ancestor" , "First Christian ancestor" , "Robert -, Sc. architect" .)