Measure of energy ultimately powering steamer at sea (3,5)
I believe the answer is:
gas meter
'measure of energy' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
'ultimately powering steamer at sea' is the wordplay.
'ultimately' says to take the final letters.
'at sea' indicates an anagram.
The final letter of 'powering' is 'g'.
'steamer' with letters rearranged gives 'asmeter'.
'g'+'asmeter'='GAS-METER'
Can you help me to learn more?
(Other definitions for gas meter that I've seen before include "Measuring device for fuel used, for heating perhaps" , "Measurer of fuel consumption" , "Fuel flow measurer" , "Domestic utility device" , "Bill after its second reading, perhaps" .)