Measure a spare part (3)
I believe the answer is:
are
'measure' is the definition.
(are is a kind of measure)
'a spare part' is the wordplay.
'spare part' becomes 're' (re is a kind of part. I am not sure about the 'spare' bit.).
'a'+'re'='ARE'
Can you help me to learn more?
(Other definitions for are that I've seen before include "Is, in the plural" , "Era (anag.)" , "(We/you/they) exist" , "is for more than one" , "live" .)