Gather inside train ferry (5)
I believe the answer is:
infer
'gather' is the definition.
('infer' can be a synonym of 'gather')
'inside train ferry' is the wordplay.
'inside' indicates the answer is hidden within the clue.
'INFER' is hidden within 'train ferry'.
(Other definitions for infer that I've seen before include "Insinuate" , "Take finer meaning from" , "Establish by deduction" , "Conclude by reasoning" , "Draw a conclusion" .)