Contaminated one in container to spread (7)
I believe the answer is:
tainted
'contaminated' is the definition.
(tainting is a kind of contaminating)
'one in container to spread' is the wordplay.
'one in container' becomes 'tain' (I can't explain this - if you can you should give a lot more credence to this answer).
'to spread' becomes 'ted' (I've seen this in another clue).
'tain'+'ted'='TAINTED'
Can you help me to learn more?
(Other definitions for tainted that I've seen before include "Spoiled, stained" , "Contaminated, polluted" , "Adulterated" , "Corrupted, sullied" , "Flawed, contaminated" .)