Power leads bad for tablet (4)
I believe the answer is:
pill
'tablet' is the definition.
('pill' can be a synonym of 'tablet')
'power leads bad' is the wordplay.
'leads' suggests taking the first letters.
'bad' becomes 'ill' ('ill' can be similar in meaning to 'bad').
The first letter of 'power' is 'p'.
'p'+'ill'='PILL'
'for' is the link.
(Other definitions for pill that I've seen before include "Lozenge" , "Medication" , "Dreadful person" , "nuisance to put up with" , "Medicinal tablet" .)