Hair of the dog technician may need (3,4)
I believe the answer is:
lab coat
'technician may need' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'hair of the dog' is the wordplay.
I cannot quite see how this works, but
'hair' could be 'coat' (coat is a kind of hair) and 'coat' is found within the answer.
'dog' could be 'lab' (short for labrador) and 'lab' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for lab coat that I've seen is " Scientist's protective clothing (abbr)".)