Jack's first person to be recruited by army (5)
I believe the answer is:
hoist
'jack's' is the definition.
(thesaurus)
'first person to be recruited by army' is the wordplay.
'first person' becomes 'i'.
'to be recruited by' is an insertion indicator.
'army' becomes 'host' (I've seen this before).
'i' going into 'host' is 'HOIST'.
(Other definitions for hoist that I've seen before include "Come down" , "Give a lift" , "Lift with ropes and pulleys" , "Raise aloft" , "Substance forming outer skeleton of insects, etc" .)