I need to add a parting gift bag (8)
I believe the answer is:
knapsack
'bag' is the definition.
(knapsack is a kind of bag)
'i need to add a parting gift' is the wordplay.
'i' becomes 'a'.
'need' says to put letters next to each other.
'to add' becomes 'ps'.
'a parting' means one lot of letters goes inside another (inserted letters split or part another word).
'gift' becomes 'knack' (knack is a kind of gift).
'a'+'ps'='aps'
'aps' placed inside 'knack' is 'KNAPSACK'.
(Other definitions for knapsack that I've seen before include "Hiker's bag" , "Bag with straps" , "Pack sank (anag.)" , "Traveller's or soldier's bag" , "Hiking bag" .)