Open old present held back (7)
I believe the answer is:
exposed
'open' is the definition.
(synonyms)
'old present held back' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'present' becomes 'pose' (synonyms).
'back' suggests the final letters (the letter at the back).
The last letter of 'held' is 'd'.
'ex'+'pose'+'d'='EXPOSED'
(Other definitions for exposed that I've seen before include "Laid bare" , "Made known" , "Without cover" , "naked" , "Uncovered, visible" .)