Cry, having starter of sour milk product (6)
I believe the answer is:
scream
'cry' is the definition.
('scream' can be a synonym of 'cry')
'starter of sour milk product' is the wordplay.
'starter of' suggests taking the first letters.
'milk product' becomes 'cream' (I've seen this before).
The first letter of 'sour' is 's'.
's'+'cream'='SCREAM'
'having' is the link.
(Other definitions for scream that I've seen before include "Indication of terror - how funny!" , "comedian?" , "Holler" , "Person who seems extremely funny?" , "Howl, shriek" .)