Amateur to take charge of weapon at the front (8)
I believe the answer is:
armchair
'amateur' is the definition.
(I've seen this before)
'to take charge of weapon at the front' is the wordplay.
'to take charge of' becomes 'chair'.
'weapon' becomes 'arm' (I've seen this before).
'at the front' means one lot of letters go next to another.
'chair' put after 'arm' is 'ARMCHAIR'.
(Other definitions for armchair that I've seen before include "Place for critic" , "It's comfortable to sit in" , "Arch Irma perched on comfortable seat" , "Sort of detective" , "TV viewer's seat" .)