Little person not getting on — we express sadness (7)
I believe the answer is:
weepers
'we express sadness' is the definition.
(I know this)
'little person not getting on' is the wordplay.
'little' becomes 'wee' (similar in meaning).
'not getting' is a deletion indicator.
'person' with 'on' removed is 'pers'.
'wee'+'pers'='WEEPERS'
(Other definitions for weepers that I've seen before include "dark coverings?" , "People crying" .)