Very small, soft cry (4)
I believe the answer is:
weep
'cry' is the definition.
(I know that cry can be written as weep)
'very small soft' is the wordplay.
'very small' becomes 'wee' ('wee' is a Scottish word for small).
'soft' becomes 'p' (musical abbreviation for 'piano').
'wee'+'p'='WEEP'
(Other definitions for weep that I've seen before include "Bawl" , "Seep slowly out" , "Greet" , "lament" , "Cry, shed tears" .)