Many loath at first to grab cross old salamander (7)
I believe the answer is:
axolotl
'salamander' is the definition.
(axolotl is a kind of salamander)
'many loath at first to grab cross old' is the wordplay.
'many' becomes 'lot' (I've seen this before).
'at first' suggests taking the first letters.
'to' means one lot of letters go next to another (I've seen this in other clues).
'grab cross' becomes 'ax' (I can't justify this - if you can you should give a lot more credence to this answer).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
The first letter of 'loath' is 'l'.
'lot'+'l'='lotl'
'ax'+'o'='axo'
'lotl' put after 'axo' is 'AXOLOTL'.
(Other definitions for axolotl that I've seen before include "Mexican native" , "Aquatic salamander of N America" , "Mexican salamander - allot ox (anag)" , "Type of salamander" , "amphibian" .)