Small picture that’s reduced by 50 per cent in album unfortunately (9)
I believe the answer is:
thumbnail
'small picture' is the definition.
(a thumbnail is a small version of a picture)
'reduced by 50 per cent in album unfortunately' is the wordplay.
'reduced by 50 per cent' becomes 'th' (I can't explain this - if you can you should give a lot more credence to this answer).
'unfortunately' indicates anagramming the letters (a bad or unfortunate spelling).
'in'+'album'='inalbum'
'inalbum' with letters rearranged gives 'umbnail'.
'th'+'umbnail'='THUMBNAIL'
'that's' is the link.
Can you help me to learn more?
(Other definitions for thumbnail that I've seen before include "Brief or concise representation" , "Brief description" , "small picture" , "This sketch is short and concise like manual appendage" , "which may be varnished?" .)