About to withdraw membership fee? That's a puzzle! (5)
I believe the answer is:
rebus
'that's a puzzle' is the definition.
(I've seen this before)
'about to withdraw membership fee?' is the wordplay.
'about' becomes 're' (regarding).
'to withdraw' says the letters should be written in reverse.
'membership fee?' becomes 'sub' (I've seen this before).
'sub' backwards is 'bus'.
're'+'bus'='REBUS'
(Other definitions for rebus that I've seen before include "Picture and word puzzle" , "Picture-letter puzzle" , "Pictorial pun - fictional detective" , "Enigmatic representation" , "Ian Rankin's Scottish detective" .)