Some captions appropriate (3)
I believe the answer is:
apt
'appropriate' is the definition.
(synonyms)
'some captions' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'APT' can be found hidden inside 'captions'.
(Other definitions for apt that I've seen before include "may be appropriate" , "Inclined; appropriate" , "Apposite, appropriate" , "Ready to learn" , "Suitable, appropriate" .)