It's put on to hide a tear, it seems (10)
I believe the answer is:
apparently
'it seems' is the definition.
(I've seen this before)
'it's put on to hide a tear' is the wordplay.
'it's put on' becomes 'apply' (synonyms).
'to hide' means one lot of letters goes inside another.
'tear' becomes 'rent' (rent is a kind of tear).
'a'+'rent'='arent'
'apply' placed around 'arent' is 'APPARENTLY'.
(Other definitions for apparently that I've seen before include "Clearly" , "so it seems" , "On the face of it" , "Seemingly" .)