Look out! It’s planted with explosives, we’re told! (4)
I believe the answer is:
mind
'look out' is the definition.
(minding is a kind of looking out)
'planted with explosives we're told' is the wordplay.
'planted with explosives' becomes 'mined' (with explosive mines).
'we're told' indicates a 'sounds like' (homophone) clue.
'mined' is a homophone of 'MIND'.
'it's' is the link.
(Other definitions for mind that I've seen before include "Brain" , "remember" , "'Out of sight, out of ....'" , "Watch - intellect" , "This can be made up" .)