Article takes it to be an old tax (5)
I believe the answer is:
tithe
'old tax' is the definition.
'tithe' can be an answer for 'tax' (historical tax paid to the church). I'm not sure about the 'old' bit.
'article takes it' is the wordplay.
'article' becomes 'the' (the definite article).
'takes' means one lot of letters goes inside another.
'the' enclosing 'it' is 'TITHE'.
'to be an' acts as a link.
Can you help me to learn more?
(Other definitions for tithe that I've seen before include "Tenth part (as tribute)" , "Offering" , "One-tenth; church tax" , "Tax to support the church" , "Ancient tax" .)