Rail cut may be cut short (7)
I believe the answer is:
curtail
'cut short' is the definition.
(synonyms)
'rail cut may be' is the wordplay.
'may be' is an anagram indicator.
'rail'+'cut'='railcut'
'railcut' anagrammed gives 'CURTAIL'.
(Other definitions for curtail that I've seen before include "Cut short (an activity)" , "Reduce in length" , "Abbreviate" , "Reduce in extent" , "Dock" .)