28 down
Desert
old
boy,
captured
by
US
soldier
(4)
Desert old boy, captured by US soldier (4)
hints
0
checks
0
hints
The definition is at the beginning of the clue.
How the clue works
Right, so desert is your definition — pointing to the Gobi, that big one in Asia. For the wordplay, take OB (that's the usual abbreviation for "old boy"), and get it "captured" by GI, which is your standard term for a US soldier — slot OB inside GI and you get G-OB-I.