Dog Henry discovered with no lead (5)
I believe the answer is:
hound
'dog' is the definition.
(hound is a type of dog)
'henry discovered with no lead' is the wordplay.
'henry' becomes 'H' (symbol for the unit of electrical inductance).
'discovered' becomes 'found' (to discover is to find).
'with no lead' means to remove the first letter (the letter which leads the word is removed).
'found' with its first letter removed is 'ound'.
'h'+'ound'='HOUND'
(Other definitions for hound that I've seen before include "unpleasant character" , "Sir Hugo's killer on Dartmoor" , "despicable creature" , "Hunting dog; harass" , "badger" .)