A little bit of headwind is perfect to start with (4)
I believe the answer is:
wisp
'a little bit of headwind' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'is perfect to start with' is the wordplay.
'perfect' becomes 'p' (this might be a standard abbreviation I've not previously seen).
'to' means one lot of letters go next to another (I've seen this in other clues).
'start' suggests taking the first letters.
The initial letter of 'with' is 'w'.
'is'+'p'='isp'
'isp' after 'w' is 'WISP'.
Can you help me to learn more?
(Other definitions for wisp that I've seen before include "Small strand of something" , "Delicate strand" , "Small streak of smoke or cloud" , "Curling bit of smoke, hair, etc" , "(Smoke) thin plume" .)