Encouragement to start releases (4,2)
I believe the answer is:
lets go
'releases' is the definition.
('let go' can be a synonym of 'release')
'encouragement to start' is the wordplay.
'encouragement' becomes 'lets' (I can't justify this - if you can you should believe this answer much more).
'to' means one lot of letters go next to another.
'start' becomes 'go' (synonyms).
'lets'+'go'='LETS GO'
Can you help me to learn more?
(Other definitions for lets go that I've seen before include "Order to leave" , "Come on then, we're off!" , "Liberates" , "Releases from one's grip" , "fires" .)