Problem that's pictured on public transport (5)
I believe the answer is:
rebus
'problem' is the definition.
(type of puzzle or problem)
'on public transport' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'public transport' becomes 'bus' (bus is a kind of public transport).
're'+'bus'='REBUS'
'that's pictured' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for rebus that I've seen before include "Puzzle consisting of pictures representing syllables and words" , "Pictorial wordplay" , "Picture-letter puzzle" , "Pictorial pun - fictional detective" , "Pun picture puzzle" .)