Start to stick pin into dawdler (5)
I believe the answer is:
snail
'dawdler' is the definition.
(I've seen this in another clue)
'start to stick pin' is the wordplay.
'start to' says to take the initial letters.
'pin' becomes 'nail' (I've seen this before).
The first letter of 'stick' is 's'.
's'+'nail'='SNAIL'
'into' acts as a link.
(Other definitions for snail that I've seen before include "Soft-bodied garden animal with shell" , "Slow slithery mollusc" , "Common garden mollusc" , "Mollusc with spiral shell" , "Its speed was emulated by Shakespeare's creeping schoolboy" .)