Groomsmen regularly got up (4)
I believe the answer is:
rose
'got up' is the definition.
(past tense of 'raise')
'groomsmen regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternating letters of 'groomsmen' are 'ROSE'.
(Other definitions for rose that I've seen before include "13 flower" , "Pink wine - flower" , "got out of bed" , "sprang up" , "Garden flower" .)