Master follows amateur into interior with weapon (8)
I believe the answer is:
claymore
'weapon' is the definition.
(type of medieval sword)
'master follows amateur into interior' is the wordplay.
I cannot quite understand how this works, but
'master' could be 'm' and 'm' is located in the answer.
'amateur' could be 'lay' (similar in meaning) and 'lay' is present in the answer.
'interior' could be 'core' and 'core' is found within the remaining letters.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
'with' acts as a link.
(Other definitions for claymore that I've seen before include "Highland weapon" , "Scots broadsword" , "pipe" , "mine, sort of" , "Scottish highlander's sword" .)