"It's nothing to write home about" (3)
I believe the answer is:
meh
'it's nothing to write home about' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for meh that I've seen before include "Not much cop" , "am I bovvered?" , "Unexciting (modern slang)" , "expression of indifference" , "Who cares" .)