Opener in difficulty to collect duck (5)
I believe the answer is:
drake
'duck' is the definition.
(drake is a male duck)
'opener in difficulty to collect' is the wordplay.
'opener in' suggests taking the first letters (the letter which opens the word).
'to collect' becomes 'rake' (raking is a kind of collecting).
The first letter of 'difficulty' is 'd'.
'd'+'rake'='DRAKE'
(Other definitions for drake that I've seen before include "Male billed" , "Aquatic bird" , "Ship" , "Elizabethan sailor" , "Male water-bird" .)