Squaddie to see detective (7,3)
I believe the answer is:
private eye
'detective' is the definition.
(thesaurus)
'squaddie to see' is the wordplay.
'squaddie' becomes 'private'.
'to see' becomes 'eye' (I've seen this before).
'private'+'eye'='PRIVATE EYE'
(Other definitions for private eye that I've seen before include "Satirical magazine - undercover detective" , "Spade, say" , "Investigative satirical magazine" , "supplement to work of police?" , "Periodical" .)