Work after month to find sea creature (7)
I believe the answer is:
Here is my best explanation:
'sea creature' is the definition.
(I've seen this before)
'work after month' is the subsidiary indication.
'work' becomes 'opus' (I've seen this before**).
'after' means one lot of letters go next to another.
'month' becomes 'oct' (Oct is an example).
'opus' after 'oct' is 'octopus'.
'to find' is the link.
(Other definitions for octopus that I've seen before include "Creature with eight tentacles", "Spineless creature", "Sea creature - pulpo on a Spanish menu", "Marine cephalopod", "Large marine mollusc", "Sea creature's tentacles served as food", "fairground ride", "Eight-armed creature", "Tentacled, shell-less mollusc" and "Scoot up (anag.)".)