Number swarming round English holiday destination (8)
I believe the answer is:
tenerife
'holiday destination' is the definition.
(Canary Island)
'number swarming round english' is the wordplay.
'number' becomes 'ten' (ten is a kind of whole number).
'swarming' becomes 'rife' (both can mean widespread).
'round' is an insertion indicator.
'english' becomes 'e' (abbreviation).
'ten'+'rife'='tenrife'
'tenrife' going around 'e' is 'TENERIFE'.
(Other definitions for tenerife that I've seen before include "holiday resort" , "holiday island" , "Fire teen off the island" , "Strange fine tree on the Spanish island" , "Largest Canary island" .)