Reserve in friendly not starting (3)
I believe the answer is:
ice
'reserve' is the definition.
(both can mean aloofness)
'friendly not starting' is the wordplay.
'friendly' becomes 'nice' (nice can mean kind or friendly).
'not starting' means to remove the first letter.
'nice' with its initial letter taken away is 'ICE'.
'in' is the link.
(Other definitions for ice that I've seen before include "Slippery surface" , "Girl's best friends" , "To put in a drink or slide on" , "engine" , "Decorate a cake" .)