Stamp collecting (9)
I believe the answer is:
philately
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">stamp collecting</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for philately that I've seen before include "Stamp-collecting" , "The hobby of stamp collecting" , "collecting small items that may grow in value" , "Collecting little stickers" , "Study of postage stamps" .)