Supplication helping to restrict return of travel (8)
I believe the answer is:
rogation
'supplication' is the definition.
(I know that rogation is a type of supplication)
'helping to restrict return of travel' is the wordplay.
'helping' becomes 'ration' (a ration is a serving or helping).
'to restrict' indicates putting letters inside.
'return of' says the letters should be written backwards.
'travel' becomes 'go' (synonyms).
'go' backwards is 'og'.
'ration' enclosing 'og' is 'ROGATION'.
(Other definitions for rogation that I've seen before include "praying for a good harvest?" , "Asking" , "Solemn petition" , "Solemn supplication (in Christianity)" .)