Behold soldier get caught by deduction (5)
I believe the answer is:
logic
'deduction' is the definition.
(thesaurus)
'behold soldier get caught' is the wordplay.
'behold' becomes 'lo' ('lo' is an archaic exclamation meaning 'look!').
'soldier' becomes 'GI' (GI can mean a US soldier).
'get' is a charade indicator (letters next to each other).
'caught' becomes 'c' (cricket abbreviation).
'lo'+'gi'+'c'='LOGIC'
'by' acts as a link.
(Other definitions for logic that I've seen before include "Strict reasoning" , "subject with 14 [ARGUMENTS]" , "Reasoned thinking" , "Reasoned argument" , "Chain of reasoning" .)