Chemical discovered in Leicestershire (5)
I believe the answer is:
ester
'chemical' is the definition.
(I've seen this before)
'discovered in leicestershire' is the wordplay.
'discovered' says the answer is hidden in the clue (remove the letters covering the answer in the clue).
'ESTER' can be found hidden inside 'in leicestershire'.
(Other definitions for ester that I've seen before include "Organic chemical compound" , "Compound formed from acid and alcohol" , "Chemical compound of acid and alcohol, found in trees" , "Fat" , "Organic compound, rhymes with court joker" .)