Pull back a little, protecting excellent new weapon (7)
I believe the answer is:
poniard
'weapon' is the definition.
(poniard is a kind of weapon)
'pull back a little protecting excellent new' is the wordplay.
'pull back' is a reversal indicator (I've seen 'pulled back' mean this).
'a little' becomes 'drop' (a drop is a small amount).
'protecting' is an insertion indicator (inserted letters are held or protected).
'excellent' becomes 'ai' (resembles 'Ad', old-fashioned term for excellent).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'ai'+'n'='ain'
'drop' going around 'ain' is 'drainop'.
'drainop' written backwards gives 'PONIARD'.
(Other definitions for poniard that I've seen before include "Slender dagger" , "A drop in (anag) - dagger" , "straight crease?" , "Thin knife" .)