He oils and changes gears with hesitation (7)
I believe the answer is:
greaser
'he oils' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'changes gears with hesitation' is the wordplay.
'changes' indicates anagramming the letters.
'with' says to put letters next to each other.
'hesitation' becomes 'er' (sound used when hesitating).
'gears' with letters rearranged gives 'greas'.
'greas'+'er'='GREASER'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for greaser that I've seen before include "Mechanic - sycophant" , "Young motorcyclist" , "Ship's engineer; motor mechanic" , "(Unskilled) mechanic" , "An unctuous individual" .)