Haul new plastic nets, getting unexpectedly lucky (6-4)
I believe the answer is:
heaven-sent
'unexpectedly lucky' is the definition.
'haul new plastic nets' is the wordplay.
'haul' becomes 'heave' (I've seen this before).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'plastic' indicates an anagram (plastic can mean easily moulded).
'nets' is an anagram of 'sent'.
'heave'+'n'+'sent'='HEAVEN-SENT'
'getting' is the link.
(Other definitions for heaven-sent that I've seen before include "Very timely" , "Coming at a very opportune time" , "Providential" , "Occurring just at the right time" .)