Movement on course, swallows fly (9)
I believe the answer is:
downswing
'movement on course' is the definition.
The definition suggests a singular noun which matches the answer.
'swallows fly' is the wordplay.
'swallows' becomes 'downs' (I've seen this in another clue).
'fly' becomes 'wing' (synonyms).
'downs'+'wing'='DOWNSWING'
Can you help me to learn more?
(Other definitions for downswing that I've seen before include "decline" , "Part of drive" , "trend towards recession?" , "worsening of economy" .)