Article given to judge or head of enquiry is for that 2 ... (9)
I believe the answer is:
therefore
'is for that 2' is the definition.
I can't tell whether this definition defines the answer.
'article given to judge or head of enquiry' is the wordplay.
'article' becomes 'the' (the definite article in English).
'given' means one lot of letters go next to another.
'to judge' becomes 'ref' (referee).
'head of' says to take the initial letters.
The first letter of 'enquiry' is 'e'.
'the'+'ref'+'or'+'e'='THEREFORE'
Can you help me to learn more?
(Other definitions for therefore that I've seen before include "In consequence" , "It follows" , "Thus" , "Consequently - for that reason" , "Ergo" .)