Provide what is required but react badly (5)
I believe the answer is:
cater
'provide what is required' is the definition.
(I've seen this before)
'react badly' is the wordplay.
'badly' indicates anagramming the letters.
'react' is an anagram of 'CATER'.
'but' acts as a link.
(Other definitions for cater that I've seen before include "Make provision for" , "Provide food etc" , "Supply food for social event" , "... you'll see minister" , "Provide for, supply" .)