Push forward (6)
'push forward' is the definition.
(to propel is to push forward)
This is the entire clue.
(Other definitions for propel that I've seen before include "Give impetus to" , "Drive or push forward as with oars" , "Launch" , "Derive of push forward" , "Cause to move forward with force" .)
'push forward' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for impel that I've seen before include "Hold together" , "Goad" , "Urge or force to action" , "'Drive, force (5)'" , "Send or drive forward" .)