Frank, off to collect learner (4)
I believe the answer is:
bald
'frank' is the definition.
(thesaurus)
'off to collect learner' is the wordplay.
'off' becomes 'bad' (I've seen this in other clues).
'to collect' indicates putting letters inside.
'learner' becomes 'l'.
'bad' enclosing 'l' is 'BALD'.
(Other definitions for bald that I've seen before include "Unadorned" , "Follicly challenged?" , "Without hair" , "Lacking hair on the head" , "Lacking hair on the scalp" .)