Finale of Blackpool's summer run (6)
I believe the answer is:
ladder
'run' is the definition.
(both can mean a rip in tights)
'finale of blackpool's summer' is the wordplay.
'finale of' suggests the final letters.
'summer' becomes 'adder' (someone who adds or does sums).
The last letter of 'blackpool' is 'l'.
'l'+'adder'='LADDER'
(Other definitions for ladder that I've seen before include "sometimes with companion" , "Hierarchical structure" , "A fire-fighter may use one" , "A run in a stocking" , "Climbing structure" .)