Limerick perhaps shortened to make an impression (5)
I believe the answer is:
count
'make an impression' is the definition.
(to count is to matter or make an impression)
'limerick perhaps shortened' is the wordplay.
'limerick perhaps' becomes 'county' (Limerick is an Irish county).
'shortened' means to remove the last letter.
'county' with its last letter taken away is 'COUNT'.
'to' is the link.
(Other definitions for count that I've seen before include "Sum up" , "Titled man" , "Matter to consider" , "Nobleman - enumerate" , "Nobleman - have importance" .)