Conceal end of elephant seal (6)
I believe the answer is:
cachet
'seal' is the definition.
(synonyms)
'conceal end of elephant' is the wordplay.
'conceal' becomes 'cache' (I've seen this before).
'end of' indicates one should take the final letters.
The last letter of 'elephant' is 't'.
'cache'+'t'='CACHET'
(Other definitions for cachet that I've seen before include "Social distinction" , "French prestige or distinguishing mark" , "Distinctive stamp" , "Feature or quality conferring prestige" , "Distinguishing feature" .)