Irish mother leave fully grown form? (5)
I believe the answer is:
imago
'fully grown form?' is the definition.
'imago' can be an answer for 'form?' (I have seen 'Form of insect' mean 'imago' so perhaps 'form' could also mean 'imago'). I'm not certain of the 'fully grown' bit.
'irish mother leave' is the wordplay.
'irish' becomes 'i' (this could be a standard abbreviation I've not previously seen).
'mother' becomes 'ma' (ma can mean mother).
'leave' becomes 'go'.
'i'+'ma'+'go'='IMAGO'
Can you help me to learn more?
(Other definitions for imago that I've seen before include "Last stage of adult insect" , "Mature insect after metamorphosis" , "picture of important person" , "Post-pupa stage of an insect" , "For example, monarch ultimately" .)