Puzzle: was soldier Jack set up? (6)
I believe the answer is:
jigsaw
'puzzle' is the definition.
(jigsaw puzzle is a kind of puzzle)
'was soldier jack set up?' is the wordplay.
'soldier' becomes 'gi' (GI can mean a US soldier).
'jack' becomes 'j' (playing card abbreviation).
'set up?' is a reversal indicator (I've seen 'set up' mean this).
'was'+'gi'+'j'='wasgij'
'wasgij' in reverse letter order is 'JIGSAW'.
(Other definitions for jigsaw that I've seen before include "Puzzle - powered cutter" , "Puzzle in which pieces must be reassembled" , "Picture in pieces" , "Sharp tool (for cutting puzzle into pieces?)" , "Puzzle fittingly completed" .)