Cry about getting an onion? (4)
I believe the answer is:
bulb
'an onion?' is the definition.
(onion is a kind of bulb)
'cry about' is the wordplay.
'cry' becomes 'blub' (I've seen this before).
'about' says the letters should be written in reverse.
'blub' backwards is 'BULB'.
'getting' acts as a link.
(Other definitions for bulb that I've seen before include "Source of flower or light" , "daffodil here" , "Growing source" , "Underground storage organ for some plants" , "shiner" .)