Boy, one often contemplated endlessly when reflecting (4)
I believe the answer is:
evan
'boy' is the definition.
(I've seen this before)
'one often contemplated endlessly when reflecting' is the wordplay.
'one often contemplated' becomes 'navel'.
'endlessly' means to remove the last letter.
'when reflecting' says the letters should be written in reverse.
'navel' with its final letter removed is 'nave'.
'nave' written backwards gives 'EVAN'.
(Other definitions for evan that I've seen before include "Welshman" , "Boy" , "boy's name" , "Man's name; vane (anag.)" , "Man" .)