Returning, young Samuel, US serviceman, adds two points for the puzzles (7)
I believe the answer is:
enigmas
'the puzzles' is the definition.
(an enigma is a puzzle or mystery)
'returning young samuel us serviceman adds two points' is the wordplay.
I cannot really see how this works, but
'points' could be 'en' and 'en' is present in the answer.
This may be the basis of clue (or it may be nonsense).
'for' is the link.
Can you help me to learn more?
(Other definitions for enigmas that I've seen before include "They're mysterious or difficult to understand" , "Puzzles - mysteries" , "'Mysteries, riddles (7)'" , "Problems" , "'Puzzles, riddles (7)'" .)