One struggles with delivery vans in small town, say, on turning up (9)
I believe the answer is:
stutterer
'one struggles with delivery vans' is the definition.
I can't tell whether this definition defines the answer.
'small town say on turning up' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'town' becomes 't' (common abbreviation eg in football team names).
'say' becomes 'utter' (to utter something is to say or speak it).
'on' becomes 're' (regarding).
'turning up' is a reversal indicator.
're' written backwards gives 'er'.
's'+'t'+'utter'+'er'='STUTTERER'
'in' is the link.
Can you help me to learn more?
(Other definitions for stutterer that I've seen before include "being prone to repetition" , "One with a speech defect" .)