Run away to marry some model openly (5)
I believe the answer is:
elope
'run away to marry' is the definition.
(I've seen this before)
'some model openly' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'ELOPE' is hidden within 'model openly'.
(Other definitions for elope that I've seen before include "escape" , "Run away together" , "Run away with one's beloved" , "Run away to wed" , "do a moonlight flit" .)