Foolish East German ignoring an indicator of fuel use (3,5)
I believe the answer is:
gas meter
'indicator of fuel use' is the definition.
(gas meter shows how much gas is left)
'foolish east german ignoring an' is the wordplay.
'foolish' indicates anagramming the letters (a foolish spelling).
'ignoring' suggests deleting specific letters.
'east'+'german'='eastgerman'
'eastgerman' with 'an' removed is 'eastgerm'.
'eastgerm' is an anagram of 'GAS-METER'.
(Other definitions for gas meter that I've seen before include "Measurer of fuel consumption" , "Bill after its second reading, perhaps" , "Measuring device for fuel used, for heating perhaps" , "Fuel flow measurer" , "Domestic utility device" .)