A blow for progress! (8)
I believe the answer is:
tailwind
'a blow for progress' is the definition.
I can't tell whether this defines the answer.
'blow for progress' is the wordplay.
'blow' becomes 'wind'.
'for' means one lot of letters go next to another (I've seen this in other clues).
'progress' becomes 'tail' (I am not sure about this - if you are sure you should believe this answer much more).
'wind' put after 'tail' is 'TAILWIND'.
Can you help me to learn more?
(Other definitions for tailwind that I've seen before include "Boost for one running" , "Favourable air current" , "Blow to back" , "It increases one's (ground)speed" .)