Sign name in tank
I believe the answer is:
scorpion
'sign name in tank' is the definition.
'scorpion' can be an answer for 'sign' (I've seen this before). I am not sure about the 'name in tank' bit.
'sign name in' is the wordplay.
I cannot really see how this works, but
'sign' could be 'scorpio' (Scorpio is an example) and 'scorpio' is found in the answer.
'name' could be 'n' (common abbreviation e.g. on forms) and 'n' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for scorpion that I've seen before include "Poisonous arachnid" , "can sting one" , "Small spider with pincers and stinging tail" , "As above (Latin)" , "Stinging arachnid - constellation" .)