How to start old aeroplane: rotate propeller (3)
I believe the answer is:
oar
'propeller' is the definition.
(an oar helps propel a boat)
'how to start old aeroplane rotate' is the wordplay.
'how to start' indicates taking the first letters.
The initial letters of 'old aeroplane rotate' is 'OAR'.
(Other definitions for oar that I've seen before include "spoon?" , "Sweep" , "Pusher" , "Rowing implement" , "I'm involved in row" .)